On the basis of deadspace multiplication theory(DSMT) numeric model and modified deadspace multiplication theory（MDSMT）model, excess noise of multi-gain-stage avalanche photodiodes with different multiplication stage and different carrier initial energy was analyzed. The effect on excess noise of different width of impact-ionization multiplication layer and electron-heating layer and different doping of electric field control layer was also studied. At the same time, the results obtained from DSMT model were compared to with the results from Van Vliet model and McIntyre model. By adjusting the width of impact-ionization multiplication layer and electron-heating layer and the doping of electric field control layer, a structure relatively optimizing was acquired by DSMT numeric simulation, the result of excess noise on of which were was comparable to the result of Van Vliet model at k_s=0.057.