The characteristics of distributed side-coupled cladding-pumped fiber laser are studied with simulation based on a coupled rate equation model. Both the distributed side-coupled cladding-pumped fiber lasers and the end-pump double-cladding fiber lasers are simulated, and the distributions of the pump light and laser of the two models are given out. Then the optimum fiber length is discussed. The results show that the pump light in the signal fiber of distributed side-coupled cladding-pumped fiber is well-distributed and the thermal load of the two ends is released. The laser is produced linearly so that the heat is dispersed to the whole fiber. It is a great advantage to be applied to high power fiber lasers and provides a new road to the higher fiber lasers.