The invention belongs to the technical field of natural ester insulating oil and particularly relates to a vacuum oil filtering process for natural ester insulating oil. The process comprises the following steps: 1) ultrasonic coalescence dehydration treatment; 2) two-stage vacuum dehydration treatment; 3) fine filtration and adsorption treatment; 4) additive addition and cyclic cooling treatment. The natural ester insulating oil filtered with the process is characterized in that the moisture content is lower than or equal to 25 ppm, the acid value is smaller than or equal to 0.015 mgKOH/g, the medium loss factor is smaller than or equal to 0.36%, the content of C2H2 is zero, and the total hydrocarbon content is lower than 1 mu L/L; the natural ester insulating oil completely meets requirements of domestic and foreign standards for the natural ester insulating oil. The whole process flow is simple, the operation cost is low, and popularization is facilitated.