The background of digital management of urban planning engineering comes from the acceleration of urbanization and the continuous rise of population density, which brings challenges to urban governance. At the same time, the development of digital technology has also provided new solutions for urban governance. The digital management system of urban planning engineering has serious inefficiency and management error rate. In this paper, K-means algorithm is used to establish the digital management system of urban planning engineering, and the conclusion is drawn through the experiment. The algorithm greatly reduces the error rate, and its accuracy rate reaches 98.6, which improves the efficiency of digital management of urban planning engineering.