The geometries of 55 organic azides were fully optimized by using the semiempirical molecular orbi- tal (MO) methods of AM1,PM3,MNDO and MINDO/3. Compared with the available experimental geometry parameters in gaseous phase,it is found that the calculation error from AM1 is the smallest and the next are those from PM3 and MNDO.Among four MO methods used, the heat of formation computed with AM1 is the closest to the results obtained from group additivity method. The results from MINDO/3 are the worst.