Advances in technology allow humans to more quickly and precisely in carrying out various activities in everyday life. One of the companies engaged in the field of vehicle washing services is Doorsmeer Keluarga Nasution. Doorsmeer. The Nasution Family Doorsmeer, located on Jl. Medan Padang Aek Godang Panyabungan, Mandailing Natal Regency, provides services in the form of car and motorcycle washing. Bookkeeping at the Nasution Family Doorsmeer is still done manually, allowing for loss of important transaction data, as well as a lack of business promotion in the community resulting in slow business development. The purpose of this study is generally to apply Web-based Customer Relationship Management with the K-means algorithm method for marketing/transactions at the Nasution Family Doorsmeer. This research is a combined type, using descriptive qualitative and quantitative methods. From the research results it is known that with the existence of Web-based Customer Relationship Management it can simplify and assist in managing good marketing strategies so that they can increase sales revenue, and by providing the best service will encourage customer loyalty and make it easier to determine loyal customers with the K-means algorithm in order to continue to provide convenience to customers.