In view of the difficulty in improving the irradiation uniformity of the current solar simulator, the paper introduces a new type of cluster- type optical integrator. The process of the cluster- type optical integrator based on the theoretical analysis of the symmetric optical integrator is introduced. The solar simulator optical system is simulated with LightTools software. The results show that: after using the cluster-type optical integrator, the irradiation non uniformity of solar simulator is significantly improved, irradiation non-uniformity in the range of Φ 50 mm is less than 0.2%, and in the range of Φ (50~120) mm is less than 1.5%. The results satisfy the requirements of high irradiation uniformity.