BACKGROUND: Operating companies and consumers have demands to vehicles for efficiency improvement and cost cut. A part of substantial expenses is fuel cost, therefore use of vehicles with electric drive such as hybrid or pure electric (battery-electric) has potential for agriculture. It is mainly important for them to have the drivetrain characterized by high efficiency that increases autonomous mileage for one charge. To achieve this, it is necessary to control electric motors in the way to ensure maximal surface grip coefficient without wheel slipping. In this case, real-time defining of wheel resistance torque in necessary for efficient control. AIMS: Development of the theoretical basis and the law of optimal estimation of the resistance torque at a shaft of traction electric motor of transport vehicles for the sake of efficient control of traction electric drive. METHODS: Simulation of the law of optimal estimation of the resistance torque at a shaft of traction electric motor was carried out in the MATLAB/Simulink software package. RESULTS: The article provides with theoretical basis of formatting the law of optimal estimation of the resistance torque at a shaft of traction electric motor of transport vehicles for the sake of efficient control of traction electric drive, the law of optimal estimation of the resistance torque at a shaft of traction electric motor and the results of simulation of the law of optimal estimation of the resistance torque at a shaft of traction electric motor obtained in the MATLAB/Simulink. CONCLUSIONS: Practical value of the study lies in ability of using the proposed control laws for development of transport vehicles drivetrain control system.