Abstract: Wax appearance temperature is an important parameter representing wax precipitation process of crude oil. Based on the traditional microscopic observation method, quantitative analysis results of wax-crystal microscopic image are introduced and the first step point temperature of crude oil wax-crystal particle number growth in the temperature drop is used to determine the wax appearance temperature in order to reduce the influences from human visual errors and dust attached to the slide and slide defect on testing results of the wax appearance temperature. Testing results from 6-kind of waxy crude oils show that this method appears a good repeatability and differences of wax appearance temperature obtained from parallel experiments all are within 2 ℃. Compared with the wax appearance temperature measured by the differential scanning calorimetry (DSC), the above wax appearance temperature range are 1~4 ℃ higher than DSC method and average wax appearance temperature value of 6-kind of waxy crude oils is 2.1℃ higher than that of DSC.