Aiming at the characteristics of pulse laser such as high peak power, low repetition frequency, limited duty cycle and so on, the existing optical wireless communication modulation schemes are analyzed and improved, symbol structure of the improved modulation schemes are given, their performance of average transmission power, bandwidth requirement, and transmission capacity are analyze and compared. Deduce the packet error rate based on the ideal additive white Gaussian noise channel model. Theoretic analysis and simulation show that pulse midth modualation has the largest transmission capacity.If it is used to modulate pulse laser, it can not only overcome the limitations of pulse laser, but also achieve good performance, so it has application mospect in optical wireless communication system to some extent.