Laplace transform is widely used and the calculation of the inverse transform is normally necessary. However, the calculation of inverse Laplace transform is considered as a paradigm for exponentially ill-posed problems. In this work, we shall introduce a new model for the calculation of inverse Laplace transform by creating an equation called leading equation, such that the solution of the leading equation is the inverse Laplace transform. The new model presents many possibilities for the calculation of inverse Laplace transform, such that any method leading to the solution of the leading equation serves as a valid method to calculate the inverse Laplace transform. We will also provide alternative ways to find the inverse Laplace transform of a rational function, which is useful in the case when the calculation method of partial fraction expansion is not effective.