The invention relates to a measurement method for a head-dismounting-free turns ratio test of an oil-oil sleeve pipe transformer. The measurement method is technically characterized in that a GIS isolation switch is disconnected, and an earthing switch is switched on; ground joint is turned on, and a turns ration tester is connected to the leading-out end of the earthing switch according to the wiring mode of a test of not connecting neutral points; the turns ratio of the transformer is measured, and the turns ratio measurement error value theta of the test of not connecting the neutral points is obtained; the value theta is substituted into the following reduction formula to obtain the actual turns ratio error epsilon of the transformer. The reason of the difference between a test of connecting neural points and the test of not connecting the neutral points is analyzed, reduction is carried out on the measurement result of the head-dismounting-free turns ratio test of the oil-oil sleeve pipe transformer, a result the same as that of the test of connecting the neural points is obtained, test time is saved, and accuracy of the test result is guaranteed.