Quantum key distribution (QKD) is a research topic of information security area. It can provide physical security key distribution. However, the low key rate of QKD limits its practical appliance. The increasement of the speed of LD driver pulse modulation effectively improves signal rate, to expedite the key generation rate of quantum key distribution. Modulation rate of 200 MHz can be achieved based on FPGA at 200 MHz clock frequency. Experiment results show that the jitter of the output quantum signal is less than 2 ns when using the scheme to generate trigger pulse to driving LD, which meets the requirements of quantum key distribution.