The circumferential scanning and tracking system used for small satellite laser communication is installed outside the satellite,and it is subjected to huge impact load during the process of satellite launching and rising.The hood connected with the locking mechanism is a key component of optical locking,the stiffness and strength of the structure directly affects the reliability of the whole machine.This paper is based on the characteristics of the circumferential laser communication system.First,the external constraints of the hood were analyzed and calculated.Under the premise of ensuring the mechanical requirements,we optimized the design of the hood by combining topology optimization and free size optimization,so as to reduce the weight of the hood.The analysis shows that the quality of the hood is reduced by 17.08%,the maximum stress and the maximum strain are reduced by 45.45% and 54.93%,respectively,and the first three order modes are also significantly improved,which improves the usability of the hood and the reliability of the whole machine.