To efficiently estimate the composition-dependent thermodynamic properties of fluid mixtures by molecular simulation, a method that adopts a thermodynamic path along a composition profile was proposed. In this method the relative values of both entropy-related properties, such as free energy, and the ensemble average properties, such as enthalpy, are evaluated as a sum of differences between neighboring composition states along the thermodynamic path. Correspondingly, a simulation with particle transitions, called the particle transition simulation, was used to sample all the composition states along the thermodynamic path. On such paths, the sampling sizes for the calculation are increased significantly because of the statistical equivalence among the particles of each component. The relative thermodynamic properties of all the composition states along the path can be calculated by this approach. This method has been used to estimate excess properties of binary and ternary Lennard-Jones mixtures in the NVT or NPT ensemble. Good agreement with other reports was found.