This paper presents some preliminary results on the modeling and simulation of Variable Air Volume (VAV) test rig in the Department of Building Engineering in UMIST .The modeling for each component such as fan , duct and VAV terminal box with their control system in the test rig has been achieved and the simulations via the logical connection of the component models have been performed by means of an HVACSIM+ platform .The polynomial curve fitting method and the artificial neural network ( ANN) technique are adopted in the modeling of non-linear characteristic of the fan connected with a high slip induction motor installed in the test rig . A　 nonlinear characteristic terminal box model based on the experimental modeling of a European box is developed which differs from the linear or exponential damper models currently available in HVAC simulations. The ANN fan model and the terminal box model are inserted in the program of HVACSIM+ as the new component subroutine. The accurate simulation results for the VAV test rig via HVACSIM+ are validated by the real system operation performance.