We propose a simple scheme for realizing multi-functional ultra-wideba nd (UWB) pulse modulation based on the gain saturation in a semiconductor optical amplifier (SO A).In the scheme, adopting only one SOA and optical source can achieve pulse shape modulation (PSM ),pulse amplitude modulation (PAM) and bi-phase modulation (BPM),which is with easy implementatio n,simple structure and low cost.By using the software of OptiSystem,the impacts of parameters and t ransmission characteristics of signal are numerically simulated and studied.The results sho w that this scheme is insensitive to the wavelength and source power change.In addition,the modulat ion signal can be transmitted for 35km in the single mode optical fiber.