The invention relates to a device for testing surface cracks of expansive soil under a moisture-heat-stress coupled effect, and a use method. The device comprises a model box, a high-strength glass plate, an expansive soil sample, a water supply system, a temperature control system, a loading system and a data acquisition system; the high-strength glass plate is arranged in the model box; the expansive soil sample is placed on the high-strength glass plate; plastic ring knives are arranged on the periphery of the expansive soil sample; the plastic ring knives and the high-strength glass plateare of transparent structures; and the expansive soil sample includes an expansive soil test sample and a parallel test sample. The use method is simple to operate, simple and convenient to adjust andeasy to control; real testing of the surface cracks of the expansive soil under the moisture-heat-stress coupled effect is realized, and meanwhile, the structure of the soil sample is prevented frombeing damaged in the testing process, so that the accuracy of a testing result is improved, the damage-free testing is realized, and a foundation is provided for moisture-heat-stress coupled researchof the expansive soil.