The static tensile test is carried out for the composite materials with delamination defects. The surface temperature variation of specimen is monitored by infrared thermography. The temperature variation of the specimen in the whole process, the damage evolution process and the relationship between heat dissipation and damage process are studied. The results show that the surface temperature of the specimen first decreases linearly and then increases continuously. When the temperature drops to the lowest point, the corresponding stress value is the yield limit of the specimen. The heat source point first occurs in the composite with delamination defects. As time goes on, the heat source area is becoming wider and wider. The thermal dissipation factor of the composite with delamination defects is 55%. The infrared thermography technology could monitor the damage of composite materials with defects. It is beneficial to the research on the engineering application of composite materials.