In measuring the steel wire rope, the key problem is to detect and eliminate the measure error for wheel spin. In order to measure the length of steel wire rope precisely, the velocity ratio of the wheel of steel wire rope and driving windlass is adopted for detecting wheel spin and the accumulated pulse error is also adopted to eliminate the round off error. Phase zero is used to remove the jam pulse of electromagnetism. The result shows the system works reliably and the measure error is less than 0.2%.