In this paper, the corrective continuity equation proposed by Ott and the momentum equation improved by Adami combine to solve two-dimensional simulation problems of droplet collisions in air. To effectively improve the calculation accuracy, the artificial viscosity equation and the artificial stress equation are derived which are suited for multi-phase flows with large density differences. This method is validated to be effective via examples of an initially square droplet under surface tension and in evolution process of two droplets in air. Droplet collisions for different Weber numbers (8.8, 19.8) and different impact parameters (0, 0.5) are simulated, all of which are compared with the results of VOF simulation. Through further calculation, distribution map of the two-dimensional droplet collision outcomes in air is obtained, which is in agreement with the experimental results. It is demonstrated that this method can be effective for solving problems of droplet collisions which are involved in multi-phase flows with large density differences, and is easily extended to three-dimensional simulation; thus it lays a foundation for further simulation of the secondary atomization in liquid rocket engines.