In order to solve the problem of performance degradation and even mechanical failure caused by fluctuation of feeding rate during the operation of full-feed peanut combine harvester in China, and the lack of basic research on feeding rate of full-feed peanut combine harvester, the structure and working principle of the pickup bench of the 4HLJ-3000 full-feeding peanut combine harvester developed by the author team were analyzed in this paper. The pickup bench is mainly composed of limited depth wheel, pressure rod, slide plate, pickup elastic teeth and screw conveyor. Based on the analysis of structure and working principle, a monitoring method of feeding rate based on the torque of power input shaft of pickup bench was proposed. Through the force analysis of the pickup bench, the mathematical relationship between the power input shaft torque and the feeding rate of the pickup bench was obtained. A working condition monitoring system of the speed input, shaft speed, torque and power of the power input shaft was designed, and the system was mainly composed of sensor unit, data acquisition, and data storage analysis. The sensor unit converts the torque and speed of the power input axis of the pickup bench into frequency signals, and the data acquisition module converts the frequency signals into torque and speed values and displays them, and transmits them to the computer for storage and analysis through RS485 bus and RS485 to USB. The data of torque and rotate speed of pickup bench power input shaft, forward speed of pickup harvester and feeding rate were obtained in different operating conditions by road monitoring tests. Linear function, power function, exponential function and quadratic function fitting regression analysis were used to obtain the function indicated the change of feeding rate with various torque based on the test results. The results showed that the quadratic function model had higher fitting precision, and its determination coefficient was 0.990. The fitting curve of quadratic function was analyzed, and the results showed that when the feeding rate was less than 3kg/s, the torque increased slowly with the increase of feeding rate, while the torque increased sharply and the rotation speed decreased with the increase of feeding rate. The model verification experiments were proposed, and the results showed that the established quadratic function model had good accuracy. The absolute deviation rate ranged from 0.42% to 2.43%, and the average deviation rate was 1.40%. The deviation rate increased with increasing the feeding rate. The field experiments also proved that there was a quadratic function relationship between feed rate and torque, and the torque deviation rate ranged from 1.90% to 3.58%, and the average deviation rate was 2.65% compared with the calculated results. This study can provide reference for the optimization design of the structure of full-feeding peanut picker and other crop pickers and the intelligent measurement and control of feed rate.