This paper contains results of biomass cutting process, where wheat straw was used. Tests was made on the prototype of the test stand, which allows to control parameters of the cutting process and based on that define its energy consumption. During the research following parameters were measured: rotational speed of electric motor, which drive rotor with set of cutting knives, electric current of supply and torque on a shaft. Tests was made for the variable humidity of the biomass and with knives with two different back-rake angles 5°, 15° and 30°. By using measured parameters, it was possible to calculate the power and the cutting force, which is necessary to disintegrate biomass. Main goal was to find an influence between a humidity and a back-rack angle of a cutting knife on the dynamic parameters of a process - power and cutting force. Presented results can be very useful in design process of a working assembly of the biomass disintegrating machines, which are directed to the energetic efficiency.