The invention discloses a method of measuring a steel rail length through an encoder measuring system and a measuring system of the steel rail length. The encoder measuring system comprises a first encoder measuring device and a second encoder measuring device. The method comprises: when the first encoder measuring device detects that a steel rail enters a first detecting area, the first encoder measuring device rises to a measuring position; when the second encoder measuring device detects that the steel rail enters a second detecting area, the second encoder measuring device rises to a measuring position; the first encoder measuring device descends when the second encoder measuring device rises to the measuring position; and the second encoder measuring device overlays the length measured by the first encoder measuring device and continues to measure the steel rail length. Therefore, the rate of equipment utilization is greatly improved, the replacing of measuring wheels, encoders and other spare parts is reduced, the processing ratio of accidents is reduced, a steel rail yield is increased, and processing efficiency is improved.