Quantitative explanation of various cell functions is still difficult, although there is a huge amount of accumulation of knowledge about the biological and physiological activities on both the molecular and cellular levels. The quantitative dynamic model, which integrates the functions of individual molecules on the computer, may provide a powerful tool to create and test the hypotheses of the mechanisms underlying the biological activities. In this study, the object-oriented methods were applied to develop the computational model of the cell function. The cell model is described as a tree structure of the functional modules that are independent of each other and exchangeable. The cardiac cell model is reconstituted of both the functional modules such as ion channels and the variables such as ion concentrations. The functional modules were classified according to the biological bases. The development of a common simulation platform will facilitate developing a large variety of cell models.