We were glad to introduce you that the 2021 3rd International Conference on Applied Machine Learning and Data Science (ICAMLDS 2021), held on 14th-16th, May, 2021, Chengdu, China. This conference was sponsored by Chengdu University of Technology and Xiamen University. Affected by the COVID-19 pandemic and the implementation of the government's isolation policy, the author was unable to arrive at Chengdu conference safely and on time. Considering the safety and health of the participants, ICAMLDS 2021 was held via online collaboration tool, Tencent meeting, which is different from the traditional way. The aim of ICAMLDS is to present the latest research and results of scientists (professors, students, PhD Students, engineers, and post-doc scientists) related to applied machine learning and data science topics. This conference provides opportunities for the delegates in different fields to exchange new ideas and experiences face to face, to establish business or research relations and to find global partners for future collaboration. We were greatly honored to have invited Prof. Xiaonan Xiao from Xiamen University to serve as our Conference Chairman. He is a professor, Ph.D. advisor, and the chair of Department of Information and Computational Science at Xiamen University Tan Kah Kee College. Professor Xiao is the executive director of Biological Mathematical Society & Mathematical Society of Fujian Province. His expertise mainly focuses on the studies of complex systems modeling and optimal control. During the conference, the conference model was divided into three sessions, including keynote speeches, oral presentations, and online QAand the last keynote speaker, Prof. Yanling Zhou, from Hamburg University of Applied Sciences, Germany and her speech title is: Big data mining and analysis based on network messages. Each keynote speech lasted for 45min including 5min for QA2) Due to age differences, online meetings are rejected by older participants. Because they are not familiar with online conferences, they need the help of others to complete their participation in the conference;3) Speakers often interrupt their speeches because multiple authors ask questions online at the same time, making the speeches not reach the best results. In the last part of the conference, all participants were invited to discuss and explore the academic issues after the presentations. The discussion was lasted for about 30-60 minutes. The conference provided a forum for discussing applied machine learning and data science and in particular for prom ting the interchange of novel ideas and the presentations of the latest developments in this field. ICAMLDS-21 received more than 179 manuscripts, and 103 submissions have been accepted by our reviewers. By submitting a paper to ICAMLDS-21, the authors understood and agreed that papers would undergo a rigorous peer-review process. Manuscripts were reviewed by at least two independent, qualified experts in the field selected by the conference committee, who took detailed comments and the authors would submit a revised version in which these feedback taken into consideration. All papers were reviewed using a double-blind review process: authors declared their names and affiliations in the manuscript for the reviewers to see, but reviewers did not know each other's identities, nor did the authors receive information about who had reviewed their manuscript. On behalf of the organizing committee, I would like to especially thank all the editors from IOP Conference Series for their great support to ICAMLDS. Finally we wish all the authors and attendees of ICAMLDS a unique, rewarding and enjoyable memory at ICAMLDS in Chengdu, China. We are looking forward to your participation in the 4th ICAMLDS in 2022. With our warmest regards, ICAMLDS 2021 Organizing Committees, General Chairs, Program Chairs, International Technical Program Committees, Sponsors, Partners and this titles are available in this pdf.