Aiming at the non- circular gear with closed pitch curve,the characteristics of pitch curves and gear tooth distribution of the non- circular gear are introduced. According to non- circular gear meshing theory and the conversion method of tooth profile,taking the limacon gear as an example,by using the Matlab software,a different eccentric pitch curve of limacon gear is drawn,and its characteristic is analyzed. The three- dimensional solid model is fully drawn,by using the function of three- dimensional solid modeling and some specific drawing instructions. According to the formation tooth profile of limacon gear,the associated features can be analyzed and the foundation of further finite element analysis,the formation of computer simulation tools trace and CNC machining are provided.