The equation of continuity of the charge carriers through a semiconductor was reduced to a second order non-linear differential equation, by using the injection-leveldependent lifetime which was derived from Shockley-Read statistics. The general solution was found using two-parameters perturbation method. The PME short-circuit current Isc and the photoconductance ΔG in a semiconductor are calculated in the second order approximation. The nonlinear properties of the photomagnetoelectric effect in the case of large signal are disclosed, experimental results are better fitted by the theory.