The coating parameters in the process of sand mold 3D printing are critical to the quality of forming sand molds. The magnitude of the sand particle size ranges from several microns to several hundred microns. Molecular forces are of obvious advantage in particle interactions. The classical Hertz contact model did not accurately describe the adhesive attraction among sand particles premixed with curing agent. The adhesive forces not only impact the quality of the sand layer but also break the formed sand mold with lower initial strength. In this paper, the Johnson Kendall Roberts (JKR) contact model in the discrete element method is used to simulate the viscous contact between sand particles with premixed curing agent. The influence of the content of the curing agent and coating velocity on the compactness of the sand layer has been experimentally researched. Through comparison of trial results and simulation results, the surface energy factor of the JKR contact model has been modified. A precise simulation model of the coating process was built. Using this simulation model, the effect of the content of the curing agent, coating velocity and scraper shape on the formed sand mold was researched. The simulation results show that higher content of curing agent and higher coating velocities have larger influence on the formed sand mold by the scraper during the coating process. In addition, the scraper with a -30° dip angle has little influence on the formed sand mold during the coating process. The results have significant engineering value and provide a theoretical guide for the process optimization of sand mold 3D printing