In view of the current employment difficulties of college graduates and the fact that the talent training program can not meet the social needs, this paper analyzes the clustering model of IT professional employment posts and knowledge needs based on decision tree algorithm. Based on big data technology, taking the employment and social recruitment information of IT majors as an example, data mining is carried out through crawler technology, and the data is crawled, cleaned and stored to obtain data sets including job, work place, salary, education, work experience, knowledge and skills. According to the feature set and data set, the ID3 algorithm is used to construct the clustering model of IT professional employment and knowledge demand based on decision tree algorithm with the goal of maximizing information gain. The experimental results show that the model can promote the scientific management and decision-making of IT talent resources, solve the employment difficulties of IT graduates in colleges and universities, and improve the level of IT talent training in colleges and universities.