Modulation scheme of atmosphere laser communication was discussed.Typical modulation schemes OOK,PPM,DPPM,DPIM and DH-PIM were introduced and its performances were analyzed.A new type of modulation called H-PPM was proposed,which was compared with the modulation scheme mentioned above.This type of modulation inherits the excellent bit error rate performance of standard PPM modulation scheme,it also need not the symbol synchronization when the information was demodulated at receiver.In this way,the design of receiver was simplified; and the difficulty of system was much reduced.Theoretical analysis and simulation results show that H-PPM is the best type of modulation for short instance,high reliability and little content laser communication between autos.