Based on the frequency response model,high frequency characteristic analysis for the TO packaged avalanche photodetectors is presented.The influence on frequency performance of TO packaging,including chip,bondwire,transimpedance amplifer,and TO header elements are investigated.By changing inductance parameters induced by different bandwires,the different frequency responses are observed.Finally,by considering the engineering conditions,a －3 dB bandwidth of 10GHz is optimally obtained for TO packaging.