The invention discloses testing equipment and a test method for soft rock filling deterioration. The testing equipment comprises a three axis instrument and a sample, and further comprises a hot air inlet system, a pumping and exhaust system, a backpressure system and a confining pressure system with external body variable measurement; the hot air inlet system is located at the bottom of the sample, the pumping and exhaust system is located at the top of the sample, the backpressure system is located at the bottom of the sample, the confining pressure system with external body variable measurement is located in a three axis pressure chamber and outside the sample. According to the testing equipment and the test method for soft rock filling deterioration, a deterioration simulation test under different confining pressure conditions is carried out, the relationship between the weathering rate and the confining pressure is established, and the optimum thickness of a protective layer for soft rock filling is determined. Through a three axis degradation simulation test, a three axis shear test for soft rock filling after full deterioration is carried out, the stress-strain relationship,failure bias stress, constitutive parameters and strength parameters and the like under different confining pressures are obtained. According to the mechanical properties of soft rock filling under different compaction degree conditions, the optimum compaction degree of soft rock filling is determined.