The invention relates to the field of measuring and discloses a system and method for measuring belt coal conveying quantity. The system comprises a scanner, a receiving device, a speed collecting device and a control device, wherein the scanner is installed on a support extending out from a coal feeder and used for measuring first cross sectional area when a belt has no load and current cross sectional area when the belt is loaded with coal; the receiving device is used for receiving the running speed of the belt; the speed collecting device is used for collecting the running speed of the coal feeder; the scanner comprises a timing device used for carrying out timing when the belt is loaded with the coal initially; the control device is used for calculating the current coal conveying quantity of the belt according to the first cross section area of, the running speed of the belt, the current cross section area, the running speed of the coal feeder and the current timing of the timing device. The system and method can effectively solve the technical problem that as a belt scale cannot be installed, the coal conveying quantity cannot be effectively measured.