Molecular thermodynamics studies thermodynamic problems at molecular level. The central task is to provide useful relations between molecular parameters and thermodynamic properties. To develop molecular thermodynamic models needed in engineering, we recommend an effective method by combining statistical mechanics and molecular simulation. Here the role of molecular simulation is not limited as a standard to test the reliability of the models. More directly, a few simulation results are used to fix partly the analytical form and the corresponding coefficients of the models. Several published examples are briefly introduced as a review to illustrate the method. A new development is also included, i.e. a new expression of Helmholtz function of mixing for compressible lattice chain fluids. Tested by simulation results indicates that the models developed can be compared with those derived by rigorous statistical mechanics or even better. On the other hand, the models developed have simpler analytical form that can be used for engineering purposes. (c) 2005 Elsevier B.V. All rights reserved.