Abstract: To clarify the dynamic characteristics of TBM hob rock breaking assisted by low-pressure abrasive air jet grooving and the influence of groove spacing. Conventional disc cutter rock breaking and low-pressure abrasive air jet grooving-assisted disc cutter rock breaking expertments were conducted. The rock failure characteristics and vertical load on the hob under the two working conditions were compared and analyzed. A three-dimensional numerical model of hob rock breaking was established using the particle discrete element software PFC^3D. The penetration and cutting process of the hob under conventional working conditions and different groove spacings were simulated. The three-dimensional crack propagation, stress evolution and hob force during the rock breaking process were analyzed. The dynamic characteristics of the hob rock breaking with the assistance of grooves and the influence of groove spacing were revealed. The results show that, before grooving, cracks were primarily distributed around the cutter blade, with tensile cracks extending toward the upper surface and interior of the rock, a “gully-like” failure morphologies were formed at the cutter indentation. After grooving, cracks were confined between the two grooves, with the propagation depth reduced. Tensile cracks propagated obliquely toward the bottom of the grooves. When the groove spacing was 65–85 mm, cracks propagated through the bottom of the grooves on both sides, resulting in two-sided rock failure, a “rock ridge-like” failure morphologies were formed at the cutter indentation. When the groove spacing was 95–105 mm, the peak stress at the bottom of one groove failed to reach the rock’s tensile strength, resulting in unilateral rock failure. Groove limited lateral stress transfer and promoted tangential stress transfer, resulting in a high stress concentration at a position obliquely below the cutter. With the assistance of grooving, the normal force and rolling force exerted on the hob during the penetration and cutting process were considerably reduced compared to the conventional working conditions. As the groove spacing increases, the maximum normal force acting on the hob, as well as the corresponding penetration depth at which rock failure occurs, gradually increase, leading to a progressive rise in both the normal and rolling forces experienced by the hob. Based on experimental and simulation results, corresponding to a groove depth of 12 mm and a width of 5 mm, for a cutter penetration of 6 mm, the critical spacing was approximately 90 mm. Using the low-pressure abrasive air jet to cut grooves within the critical spacing helps enhance the rock breaking effect of the cutterhead and improve TBM tunneling efficiency. Reserach results provide a reference for optimizing cutterhead structure design, and promote the development and application of low-pressure abrasive air jet grooving-assisted TBM rock breaking technology.