The work aims to study the effect of solid particle collision on erosion in gas-solid flow. Eulerian-Lagrangian method was used to solve the gas phase as a continuous phase by Navier Stokes equation, while the particle motion was solved by discrete phase model (DPM). The direct simulation Monte Carlo (DSMC) method was used to calculate the collision between particles. A small number of sampled particles were used to replace the real particles to calculate the collision between particles. The collision conditions were determined by the modified Nanbu method. The collision process followed the dynamic model of the collision between particles. The Grant-Tabakoff model for particles-wall collision rebound was used to calculate the collision motion between particles and wall. The particle motion information was introduced into five different erosion models, and the erosion prediction results of whether to calculate the collision between particles were compared with the experimental data. The location of particle to particle collision was mainly in the high concentration area of particles on the outer arch side of 90° elbow. With the increase of particle mass flow rate, the number of particle collisions increased, and the proportion of collision times in straight pipe section increased. With the increase of inlet velocity, the number of particle collisions decreased. The maximum erosion position calculated by DSMC-CFD method was shifted to the high angle direction along the outer arch axis of the elbow, and the numerical value was about 5%~15% lower than that of CFD method, which ignored the collision between particles. The total erosion rate by two methods had no large difference. Therefore, the calculation of particle collision by DSMC method can save a lot of effort. DSMC-CFD erosion prediction method is more practical for the particle corrosion at the elbow, and the results of Oka model using DSMC-CFD method are the closest to the experimental data.