Abstract: In order to reduce the calculation error of the lost time by the wire-line core technique, with the function calculation conducted on the relationship betwee n the core lifting speed, the pressure in the sample, the desorption speed and the core lifting time, the relationship formula between the core lifting time, radius of the wi nchtire, revolution of winch, depth of the coal reservoir, exposure time and the lost during the wire-line core process with the constant speed winch was obtained.The re sults showed that the lost time calculated with the formula could revise the error caused by the radius of the winch tire and the error would be taken 5% to 10% of the or iginal lost time.Under the conditions when the seam depth was 1 000 m, the core lifting time was 20 min and the radius ratio of winch before and after the core lifting wa s 1 :3, the revised error of the lost time would be about 2 min.Meanwhile the gas value lost and calculated error of the gas content could be reduced and the accuracy of the experiment data could be improved.