A non-standard ellipsoid condenser design method based on the binomial expansion is proposed in order to improve the effective concentration efficiency of the condenser for the solar simulator. This method controls surface shape of the condenser by changing the quadratic coefficient of the expansion. The non-standard ellipsoid condenser enhances the ability to converge defocused light energy, and improves the effective energy utilization by making the energy distribution more compact on the second focal plane. An ellipsoid condenser is used to analysis and simulate to display the actual lighting by Monte Carlo ray tracing method. Simulation results show that concentration efficiency of the non-standard ellipsoid condenser is about 10% higher than standard ellipsoid at the effective area.