Mechanically stacked AlxGa1-xAs/InP/Ge MJSC' sensitivity to SI and temperature variations was simulated. MATLAB code was using to the system received and spectra transmitting of separately z-matrix, while PC1D code modelled the energy generation. Multiplying the AM1.5d spectrum by values of SIMF (1- 200 suns) yielded the ISR on the foremost z-matrix. Temperatures of 25- 100 °C were used in each simulation run. In contrast to the stochastic response of the SCEs brought about by the SIMF changes, the simulation findings show that the V_OC and efficiency of the SCs behave linearly changes in temperature. The results of the simulations also show that the optimal performance is achieved with an irradiance spectrum exposure of 100 suns and a functional temperature of 25 °C.