Based on the dynamic trappedoil model, in order to fully reflect the superiority on Dymola in modeling and simulation, combined with objectoriented nature and noncausal nature and fully used graphical modeling features of Dymola, the problem of parameters seamless exchange between machine system and fluid system involved in dynamic trappedoil model was solved. By the modification of the existing standard library model of Dymola, from these new created component models of trappedoil volume, trappedoil flow, leakage flow and onedimensional rotation and etc., the Dymola simulation model based on existing dynamic trappedoil model was built, and the simulation results from parameters of actural situation more in line with the experimental ones was obtained. The conclusion shows that using the Dymola language is effective and feasible for the simulation of trappedoil pressure.