The invention relates to a vacuum-pumping oil injecting device. The vacuum-pumping oil injecting device comprises a first valve, a second valve, a third valve, a handheld pipe fitting and a vacuum meter, wherein an oil inlet and a vacuum pump connecting port are respectively arranged in the two ends of the handheld pipe fitting; an oil pressure buffer connecting port and the vacuum meter are arranged in the middle position of the handheld pipe fitting; the oil pressure buffer connecting port is arranged at one end, which is close to the oil inlet, of the handheld pipe fitting; the vacuum meter is arranged at one end, which is close to the vacuum pump connecting port, of the handheld pipe fitting; the first valve is arranged between the oil inlet and the oil pressure buffer connecting port; the second valve is arranged between the oil pressure buffer connecting port and the vacuum meter; and the third valve is arranged between the vacuum meter and the vacuum pump connecting port. The device is small and convenient to carry and has the advantages that oil can be rapidly injected into an oil pressure buffer during opening; and if the needed vacuum degree is not achieved before the oil injection, the vacuum degree among sections can be detected through the vacuum meter before the oil injection and which section is poor in air tightness is rapidly found to solve the problem.