Based on a hydraulic crane, a three dimension model was built in UG software, and it was imported into a dynamics simulation software ADAMS to obtained a virtual prototype model of the hydraulic crane. The hydraulic controlling model of the crane was built with EASY5. The cosimulation with mechanic and hydraulic system of the hydraulic crane was completed through the designed data interface of the software. The results show that the prototype model and the hydraulic model can be connected seamlessly and the method of cosimulation is effective and practical.