A contact model for discrete element simulation was established to obtain the physical parameters and contact mechanical parameters of viscoelasticity loam soil particlesin southern region. Take the loam soil which test measured soil repose angel 40.95° as study object, chosen Hertz–Mindlin with JKR as contact model, the loam soil physical parameters was obtained by experiment. The steepest ascent test was used to obtain the optimum contact mechanics parameters by means of soil contact mechanic parameters primary select range in GEMM database. Design–expert software was used to carry out 4 factor 3 horizontal quadrature rotation combination test to obtain repose angel regression model. The variance analysis result showed that the optimization combination parameters as follow: JKR surface energy was 13.05 J/m2, recovery coefficient was 0.5, rolling friction coefficient was 0.15, static friction coefficient was 1.06 when the actual measurement repose angle was selected as target of 40.95°. The simulated mean repose angle was 41.07 ° by using best combination parameters. The repose angle value error was 0.3% compared with actual measurement value.