Based on the instantaneous high-pressure(IHP) produced by high-pressure single pole-cylinder pump, the effects of combining this pressure with medium temperature on the retention of total vitamin C(Vc) in wax gourd juices were investigated under 20-80 MPa, 35-58℃, pH 3.0-6.0 and processing time 0-8 min. Results showed that the loss of Vc increased with elevated processing temperatures (50 MPa, 4 min). When the temperature of raw juices was 35℃, the retention of total Vc was higher under 40-60 MPa than that under the pressure ＜ 40 MPa or ＞ 60 MPa, and it was up to 94% (4 min). The retention of total Vc decreases slowly within 6 min, but rapidly after 6 min. The pH can also influence the retention of total Vc, and this retention can come to a highest point at pH 6.0.