Abstract: During the curing process of composites, residual strain will inevitably occur, which will change continuously with the curing of composites, and residual strain is the main reason leading to the final curing deformation of materials. The concentration of residual strain may cause cracks and lamination of composites, which will bring difficulties to the assembly of composite components and affect the performance of components. It is of great significance to study the in-situ detection method of curing residual strain of composites. In this study, a strain gauge in-situ detection method for curing residual strain of composites is established, and a piece-wise curing residual stress and strain gauge data processing method is proposed. The curing of composites is divided into two stages at the gel point of composites. For these two stages, different processing methods are adopted for in-situ strain gauge detection data. The strain changes in the direction of 0° and 90° were measured and compared with the results of fiber Bragg grating (FBG) in situ, which revealed the formation mechanism of the cured residual strain of the composite. The results show that the piece-wise processing of in-situ strain gauge data is basically consistent with the results of FBG, which can effectively analyze the evolution law of residual strain during solidification of composites.