Abstract: In the experiment using Faraday cup to calibrate absorbed dose of proton in alanine dosimeter, it is necessary to consider the influence of pipes, wall and other matters. To improve the accuracy of measurement, FLUKA Monte Carlo software was employed to simulate proton transport in pipes. Simulation results prove that alanine dosimeters can be irradiated uniformly if proton beam is passed through the Ta scatter film. The actual number of proton passed through alanine dosimeter is a little greater than determination by the Faraday cup. Modifying factor is gained which is 1.014. Proton energy spectrum distribution was simulated. And the average collision stopping power of proton in alanine dosimeter was calculated subsequently. Through simulation and modification, more accuracy experiment data were gained. The calibration curve of alanine dosimeter irradiated by proton was obtained at last. The linear coefficient is 0.999 5.