This paper expounds the principle of the Alaw 13segment nonlinear quantization encoding/decoding algorithm.The top floor principle diagram,simulation result and the key code of encoding/decoding part are given by using Verilog HDL language on QuartusII software platform,and the encoder/decoder can be downloaded and tested via field programmable gate array(FPGA)so that realtime speech signal transmission is implemented.The implementing process is better optimized and simplified based on the characteristics of successive approximation type algorithm so that its application has better reliability and timeliness.