We have demonstrated the theory of utilizing internal two-photon-induced light absorption of semiconductor GaAs to accomplish Q-switched pulse lengthening. The rate equations are solved and the experiments are performed with an electrooptic Q-switching Nd:YAG laser with a GaAs sample in its cavity. As predicted by the theory that the output intensity and output energy both decrease and pulse length increases as compared with the normal Q-switched case. We were able to obtain pulses as long as 1～μs.