The invention provides a load capacity measuring method and device of a construction vehicle. The method comprises the steps of: obtaining a pressure measurement value in a hydraulic oil pipe during ajacking process of the construction vehicle, wherein the hydraulic oil pipe is connected with a hydraulic oil pump for controlling to jack up the construction vehicle; drawing a curve according to the pressure measurement value in the hydraulic oil pipe, and determining a final pressure value in the hydraulic oil pipe according to the curve; and obtaining a load capacity measured value of the construction vehicle according to a predetermined function relationship between the final pressure value in the hydraulic oil pipe and the load capacity measured value of the construction vehicle. By adopting the load capacity measuring method and device provided by the invention, automatic measurement of the load capacity of the construction vehicle is realized, the measuring method is simple and convenient, and the test efficiency is high.