Scum and crust can be easily formed in the upper part of fermentation liquid, leading to low efficiency of methane production, when the corn straw is used as the main raw material for the anaerobic fermentation. In this study, an anti-crust resistant reactor was designed to inhibit the formation of the crusty layer during anaerobic fermentation. Two steps were divided into the working principle and key components in the device. Firstly, a shell-breaking device was developed as follows. A motor was selected to transmit the power into the commutator box in the planetary frame, where the box was also rotated without the power. The speed difference between the transverse stirring shaft and the input shaft was provided an effective stirring and breaking of the scum layer. Secondly, the parameters of key components were determined, including the kinetics of the shell-breaking device and the mixing blade mounting angle. An Adams platform was utilized to simulate the dynamics of the shell-breaking device and the force analysis of the stirring blades. The transmission ratio of the shell breaking was determined using the simulation. The kinetic analysis showed that the unit was operated smoothly under the optimal conditions. The force analysis of the mixing blades showed that the power consumption and the resistance of the blades were minimized at the mounting angle of 30°. A coupled DEM-CFD simulation was also used to further determine the flow and particle fields of the inclined propeller blades. The numerical simulation results showed that the rotation of the inclined paddle blade was produced an axial and radial flow of particles. The axial flow particles increased with the wall after touching the bottom, combining with the axial flow generated by the propulsive stirring blades, further to form a vortex for the upper layer of straw downwards along the vortex path. The radial flow increased the velocity of lateral movement of particles, where a wide range of lateral flow in the flow field greatly contributed to destroying the crust layer of floating slag. Taking the corn straw as the raw material for the anaerobic fermentation, a field test was conducted to verify the effect of the anti-crust reactor on the inhibition of the crust layer of floating residues. A three-factor and three-level optimization was designed, where the rotating speed, stirring interval, and single stirring time of the crust breaker were selected as the three factors, while the thickness of the scum layer was selected as the index of investigation. The results showed that the thickness of the crust layer was 16.1 cm, which was 36.1% less than that of the control crust layer of 25.2 cm, where the spindle speed of the crust breaker, the stirring interval, and the stirring time were set as 120 r/min, 3 h, and 30 min, respectively. The anti-crust reactor significantly improved the crusting of straw anaerobic fermentation. The finding can also provide a new idea for the subsequent development of anti-crust anaerobic fermentation reactors.