The rocket sled loading technique is very important for rocket sled experiment.The rocket sled running process was estimated by fourth-order Runge-Kutta based on rocket’s fitting force curve and average force curve applying with the aerodynamics theory.The velocity history and displacement in the supersonic running process were calculated,and the maximum velocity and the derailment velocity were achieved.The estimated results are well in accordant with the experimental results,which indicates that the calculated results based on fitting force curve can reflect the rocket sled running process very well.