The 2021 4th International Symposium on Big Data and Applied Statistics (ISBDAS2021) was successfully held on May 21-23, 2021 in Dali, China. ISBDAS2021 is to bring together innovative academics and industrial experts in the field of Big Data and Applied Statistics to a common forum. The primary goal of the conference is to promote research and developmental activities in Economic Management and Informatics and another goal is to promote scientific information interchange between researchers, developers, engineers, students, and practitioners working all around the world. The conference will be held every year to make it an ideal platform for people to share views and experiences in Big Data and Applied Statistics and related areas.The conference model was divided into two sessions, including oral presentations and keynote speeches. In the first part, some scholars, whose submissions were selected as the excellent papers, were given 15 minutes to perform their oral presentations one by one. Then in the second part, keynote speakers were each allocated 30-45 minutes to hold their speeches. In this conference, we were greatly honored to have invited Prof. Badrul Hisham bin Ahmad from Universiti Teknikal Malaysia Melaka and Assoc. Prof. Marina Yusoff, Universiti Teknologi MARA, Malaysia as our Conference Chair. There were over 115 experts and scholars in the area of Big Data and Applied Statistics representing different famous universities and institutes around the globe to attend the conference.During the conference, we were pleased to invite three distinguished experts to present their insightful speeches. Prof. Hua Wang, our first keynote speaker, from Shenzhen Technology University, China. His research interests: International Financial Market, Financial technology, Derivatives / quantitative trading, Financial supervision. The second keynote speaker, Assoc.Prof Pavel Loskot, from ZJU-UIUC Institute. His current research interest focuses on problems involving statistical signal processing and importing methods from Telecommunication Engineering and Computer Science to other disciplines in order to improve the efficiency and the information power of system modeling and analysis. Assoc. Prof. Sahil Verma, our finale keynote speaker, from Chandigarh University, Mohali, India. He had outstanding research in VANET, Wireless Communications, Machine Learning, Artificial Intelligence, Security, Medical Diagnostic System and other related area.List of Committee member are available in the pdf.