Fracturing construction in unconventional reservoirs in North America shows that when pumping proppant, the output is close to that of the two methods of sand addition: constant sanding and stepped sanding, with the former having more advantages in reducing the construction difficulty and saving the amount of high viscous fluid. However, there is a lack of quantitative evaluation of the difference in proppant placement effect between the two methods, and there is a lack of theoretical support for the large scale application of constant sanding. Based on computational fluid dynamics and discrete element coupling method, a numerical model of proppant transport in complex fractures with rough walls and different angles of branching fractures was established, and the accuracy of the numerical model was verified by comparing with the published experimental results, and comparative experiments of constant sanding and stepped sanding with different construction parameters were carried out. It is found that the overall difference in sand dune morphology between constant sanding and stepped sanding in the main and branch fractures is not significant, and constant sand addition has a slight advantage in filling the distal end of the main fractures and the branch fractures of the far well. As the sand concentration increases, the difference in sand dune morphology between the two types of sand addition decreases: the difference in sand dune support area is 5.96% at 10% sand concentration and 4.02% at 15% sand concentration. The difference in sand dune morphology between the two sand addition methods increased with increasing steps: 4.02% difference in sand dune support area for pumping with small steps (10% + 15% + 20%) and 7.82% difference in sand dune support area for pumping with large steps (5% + 15% + 25%) at 15% sand concentration. Increasing the viscosity can increase the effect of the two sand addition methods on the sand dune morphology. The research results can provide theoretical guidance for the optimization of field fracturing construction parameters.