This paper proposes a computer system that simulates product life cycles dynamically. A feature of the system is its ability to restructure life cycles, by which an additional module for simulation is inserted into the system when needed. This allows users to carry out various assessments efficiently depending on their purposes. To do so, a prototype system on computer program was developed and it proved the system's effectiveness through application to an example life cycle of a product, a refrigerator. Especially, it was confirmed that the system is able to calculate environmental burdens in a time series depending on given product life cycles. In addition, the system was proved to carry out simulations additionally with consumers' buying activities on the market and manufacturers' revenues and expenditures. This system is also expected to increase the efficiency of developing such systems.