Abstract: Composite materials are widely used in various fields, such as aerospace, electronics, and medicine, due to their excellent performance. However, during the production and application of composite materials, damage such as cracks, voids, delaminations, and disbonds occur inevitably, seriously affecting composite material's use safety. Therefore, the damage detection of composite materials is of great significance. Microwave imaging has advantages such as non-contact, real-time, efficient, and high contrast. At the same time, the microwave time reversal algorithm can provide the advantages of auto-focus and high resolution for microwave imaging. Therefore, microwave imaging based on the microwave time reversal algorithm has great potential in the nondestructive testing of composite materials. This paper was based on the microwave time reversal algorithm and the integral energy method to detect small buried damage in composite materials. The influence of different sensor arrangements and numbers on the detection results were studied. The key factors to improve the quality of results were discussed, and the detection of small buried damage in composite materials was achieved.