To study the impact of inlet and outlet pressure parameters on the reverse circulation cutting transport and wall erosion in micro-pile drilling rigs, a gas - solid two - phase flow simulation model for the reverse circulation cutting process in micro-pile drilling rigs was established using Fluent's Discrete Phase Model (DPM). The model analyzed the effects of different inlet and outlet pressures on the number of particles ejected from the outlet and on wall erosion by particles. The simulation results indicate that the number of rock cuttings particles exiting the reverse flushing outlet correlates directly with the pressure difference between the inlet and outlet pressures. Particle accumulation is prone to occur at the corners where three flow channels merge into the main channel. When the inlet pressure is 0.05 MPa and the outlet pressure is − 0.013 MPa, the minimum particle concentration is 0.013 kg/m3, and erosion at this location is most severe. As inlet and outlet pressures increase, so does the erosion rate on the three walls. When the inlet pressure is 0.05 MPa and the outlet pressure is − 0.01 MPa and − 0.013 MPa, the minimum erosion rate is 1.0 × 10⁻1⁰kg/m2/s. These findings are highly valuable for evaluating the performance of relevant drilling equipment, optimizing the design of cutting transport channels, and improving construction parameters.