The invention discloses a method for quantitatively testing the total concentration of small molecules in composite insulator silicone rubber. The method includes the following steps that 1, a composite insulator silicone rubber sample is selected, and small molecules in the silicone rubber sample are extracted till complete extraction; 2, extraction liquid merging is performed, and the volume is made constant after concentration; 3, extraction liquid is taken, a gas chromatograph is adopted for performing sample introduction to obtain a chromatogram of the silicone rubber sample, the peak position and retention time of each chromatographic peak are marked, and the peak area of each chromatographic peak is calculated; 4, an external standard substance is selected, a group of solutions with a concentration gradient are prepared, and a concentration-peak area standard curve of the external standard substance is made; 5, the concentration of each chromatographic peak is calculated according to the concentration-peak area standard curve of the external standard substance in the step 4 and the peak area of the corresponding chromatographic peak in the step 3, the concentrations of all the chromatographic peaks are added, and then the sum is the total concentration of the small molecules in the composite insulator silicone rubber. By means of the method, the total concentration of the small molecules in the composite insulator silicone rubber can be quantitatively tested.