The existing mathematical analysis approaches for the management of product manufacturing process cannot satisfy the global optimization and high feasibility required for product manufacturing. Neither do they reflect the actual production situation accurately and comprehensively. Therefore, this paper explores the simulation and modelling of management decisions in multi-variety small-batch product manufacturing process in discrete production environment. Firstly, the management knowledge in product manufacturing process was expressed mathematically, and the product manufacturing system was modelled in discrete production environment. Then, the flow of the interactive simulation model was explained, along with the realization steps of the model. Taking a real multi-variety small-batch production unit as the engineering background, an empirical analysis was carried out to detail the interactive simulation of the line change management for the production lines in the management system of the product manufacturing process, and to build a simulation model for the product manufacturing system. The simulation model was proved effective through simulations.