To study the static tensile performance of composite bolt connection structures in humid and hot environment, static tensile test and SEM scanning test were conducted on three types of T300 carbon fiber composite single-lap single-bolt joints with different clearances. The changes in ultimate failure load of different clearance joints under 25 ℃ dry state (RTD) and 70 ℃ equilibrium moisture absorption (ETW) environments were obtained, revealing the microscopic failure mode of the joints. The finite element models of composites single lap bolted joints were established to analyze the stress states of the laminates. The results show that when the diameter ratio increases from 0 mm to 0.2 mm and 0.4 mm, the ultimate failure load of the connection structures in the RTD environment decreases by 2.78% and 3.45%, respectively. The ultimate failure load of the connection structure in the ETW environment decreases by 4.64% and 5.01% respectively. Compared to the RTD environment, the ultimate load of connection structures with clearances of 0 mm, 0.2 mm, and 0.4 mm in the ETW environment decreases by 9.34%, 11.07%, and 10.81%, respectively. The damage around the holes in ETW environment is more severe, while the fracture surface of the substrate is relatively rough, the cracks are more obvious. And it could also find some fiber bundle pulling and fiber fragmentations. In the thickness direction of the laminated board, it could be noticed that there is less adhesive resin, and the fiber distribution morphology is relatively flat.