The Neurospora biorhythm model is based on the negative feedback auto regulation of gene expression. This research is about the comparative mathematical model for Neurospora process which specific effects on light only and on light with the FRQ protein. The models are analyzed by a differential equation theory, to find equilibrium points, the stability and the limit cycle state. The Routh-Hurwitz criterion is used for finding the parameters that confirm each state. Besides, we can verify all values of the parameters by using numerical method and solution curves.