The concentrating solar simulator can obtain solar radiation spots with high-power convergence, which has important applications in the fields of solar thermal power generation and thermochemical research. To obtain uniform solar radiation spots, a free-form surface condenser design method based on non-imaging optics is proposed, and its design principle and specific method are described. The designed free-form condenser is compared with a non-coaxial ellipsoidal condenser with the same containment angle, and the correctness of its design method is verified by simulation analysis. The simulation results show that when a xenon lamp with a rated power of 6 kW is used as the light source, the single-lamp solar simulator composed of a free-form condenser can produce a spot with an average irradiance of 274.4 kW/m² in the target region with a diameter of 60 mm. The spot’s unevenness decreases from 18.28% to 5.69% compared with that of a non-coaxial ellipsoidal solar simulator. The seven-lamp solar simulator can produce a spot with an average irradiance of 1.65 MW/m², with a spot unevenness that decreases from 13.19% to 5.49%.