In this paper,we analyzed and quantified noise behavior of QW-LDs by improving the rate equations with an added phase equation and Langivin noise.By the way,quantum noise,especially the phase noise that effects parameters such as linewidth,can be systematically represent.We simulated the noise behavior of SQW-LDs and some useful results were obtained about the phase noise spectrum and lasing property.We found that in the frequency range of interests,there is significant noise and it depends strongly on the level of the drive current as expected.