Link travel time function acts an essential role in both operational and planning intent of traffic simulation. It is also a key component in dynamic traffic assignment to capture the traffic dynamics concerning about time-varying traffic states, time-space propagation, and their interdependences. A procedure of calculating link travel time based on the numerical simulation of hyperbolic traffic flow is developed in this paper. The passage of traffic within a link is traced according to uniform partitioned meshes in a time-space plane. Traffic movements in each grid cell are decomposed into three states: entering state, intermediate state, and leaving state. Travel time in each state is calculated by using the approximations of finite-difference-based numerical results for the corresponding grid cells. These travel times of minute grids are collected to build the travel time of a link. Finally, a numerical example is illustrated to show the verification of the proposed method.