The theoretical model of all optical wavelength conversion based on an erbium-doped nonlinear amplifying fiber loop mirror is proposed. We focus on the peak power, pulse width, extinction ratio of conversion optical pulse and the transmission property of conversion optical pulse in standard single mode fiber. The results show that the conversion optical pulse has higher peak power and extinction ratio and shorter pulse width by using the model, and positive chirp is linear in the middle part of the conversion pulse. When the conversion optical pulse is transmitting in standard single mode fiber, the peak power will first increase then decrease, and the variation of pulse width is opposite as peak power.