In the learning of online course C Language Programming, the interaction between teachers and students is poor, and the teaching efficiency is low. It is difficult for students to solve the common code defects in programming themselves. To better help students solve the problems in learning and assist teachers to achieve the teaching purpose, this paper develops a practical system to assist students in programming. Firstly, the system classifies the common code defects, focusing on the analysis of syntactic, morphological and semantic defects that are not easy to detect by the compiler. Secondly, it builds an intelligent analyzer that integrates a variety of detection tools to store the set of knowledge rules and extend the abstract pattern of common code defects. Finally, it detects the codes and gives error reports and modification suggestions. This system is capable of assisting students in programming by cooperating with the student model. The experimental results show that the system can successfully detect common code defects and thereby assist students in programming practice.