A kind of tunable frequency-selective converter based on nondegenerate four-wave mixing (ND-FWM) in semiconductor laser amplifier (SLA) is proposed in this paper.The coupling model of the frequency-selective converter in SLA is established first,and then the converting mechanism and characteristics are analyzed.The influences of its property parameters on the output efficiency,and the frequency shift are primarily discussed.And the property of the output noise of the frequency-se-lective converter has been studied as well.The superior performance of the converter,such as short response time,high conversion efficiency,and large conversion range,makes it favorable for use in DWDM networks where high speed and tunableness are required.