The loading effect on high-photocurrent photodiode is studied based on equivalent circuit model.Fast and precise tuning of the load of photodiode is realized with the automated load-pull system,and the voltage swing changes due to variation in load impedance and their influence on saturation current and response bandwidth are investigated.Both the theoretical and experimental results show that the saturation current and bandwidth of a photodiode can be improved by reducing its load.It can be expected that the enhanced photodiode performance can be obtained by adopting the reduced load resistance according to application requirements.