Abstract: In this work, several liquid specific heat capacity measuring methods were introduced. The effect of temperature,viscosity,refining depth and hydrocarbon composition on the specific heat capacity of transformer oil were investigated using the measuring methods. It is found that the repeatability of flow calorimetric method（ASTM D2766—1995） with the deviation less than ±2%, is better than that of the differential scanning calorimetry (ASTM E1269-2005) method. The investigation finds that the specific heat capacity of transformer oil increases linearly with increasing temperature in the range of -20—100 ℃. The heat capacity of the oils by traditional solvent refining is hardly affected by refining depth and additives. The test results show that for the oils with the same viscosity but different aromatic contents, the heat capacities are basically the same and that the heat capacities are directly related to alkane content but increases slowly with temperature for the higher alkane content oils. As a result, the heat capacities of the oils with different alkane content are very close at 100℃. While for oils from the same oil sources, refining process and having similar carbon type composition but different boiling range, even the viscosity increases three times, the heat capacity only increases 2.6%，indicating the slightly increase of heat capacity with viscosity..