A high speed and high reliable underwater optical communication transceiver system based on digital signal processor (DSP) is proposed, and the modulation timing sequence and signal processing procedure is analyzed. In the transmitter, the DSP accomplishes Reed-Solomon codes encoding of the information need to be sent and filtering, threshold decision, the decoding and demodulation of the received information. The field-programmable gate array (FPGA) accomplishes the modulation of the information encoded in the DSP. Under the condition that the pulse width after underwater propagation is less than 100 ns and the frequency deviation from the mean is less than 15%, the dependence of the pulse position modulation (PPM) modulation rate on the chosen Galois field is discussed and the signal processing speed as well as the interfaces communication speed are analyzed. The analytical results show that the designed transmitter system can accomplish full-duplex and real time communication with a speed as high as 73 kbit/s, which can be used for real-time communication of multi-media information, such as voice and images. The pulse shape of laser after a propagation of 100 m in case Ⅱ water is simulated through Matlab as well as the timing sequence of a frame of data transmitted through FPGA and sampled sequence of a frame of data obtained through analog-to-digital converter (ADC). The structure of the designed transceiver provides a certain reference to the design and accomplishment of underwater optical communication system in the future.