Abstract: The mathematical model for prediction of radiation dose in the cabin of manned spacecrafts on near-earth orbit is complied according to 95 set LiFmeasured data and their flight orbital parameters. The model indicates that the dose level in cabin is affected mainly by orbit altitude, with a quadratic curve in this model. The solar flare activity is another factor and the effect of orbit inclination seems no importance. The predicted safe flight time is given by this model, and the radiation protection is also discussed in this paper.