A novel equipment for measuring the elastic wave velocity of rocks under various temperature and pressure conditions of ultra-deep reservoirs has been developed. The equipment consists of a high pressure and high temperature experimental platform and an ultrasonic measurement system, which can measure the elastic wave velocity of rocks under conditions of ultra-deep reservoirs up to a depth of 13 km by the ultrasonic reflection method. The method of assembling rock samples has also been improved to acquire high-quality ultrasonic signals. The feasibility of the new equipment was tested by measuring the elastic wave velocity of dolomite and limestone. The experimental results are consistent with the previous research. The elastic wave velocity of rocks measured by this equipment can be potentially used for the exploration of ultra-deep oil and gas resources.