The present invention provides a downhole auxiliary drilling apparatus, including an impact energy generator capable of converting the energy of the drilling fluid to the axial impact energy, and an impact energy distributor capable of redistributing the impact energy generated by the impact energy generator to convert the axial impact force into a combined impact force, which provides the drilling bit with a high-frequently changing combined impact force, thus greatly improving the rock breaking efficiency and the rate of penetration of the drilling tool. The downhole auxiliary drilling apparatus is further provided with a shock-absorbing and torque-stabilizing device arranged between the impact energy generator and the impact energy distributor, which can reduce the axial vibration of the drilling tool and the damage on the drilling bit, and greatly extend the lifetime of the drilling bit.