The invention relates to a method for determining temperature field distribution of a cabin of a carrier rocket in a flight phase in an atmospheric layer. The method comprises a first step of determining an aerodynamic heating thermal flow qh changing along with the flight height and acting on the outer wall of the cabin; a second step of determining an average natural convection heat transfer coefficient alpha n of the shell surface of an instrument in a closed cavity of the cabin changing along with the flight height; a third step of determining a forced convection heat transfer coefficient alpha f of interior of the cabin caused by flight accelerated speed and constant leakage of gas in the cabin; and a fourth step of building a cabin node thermal network model, finishing thermal coupling analysis, and obtaining the cabin temperature field distribution. The method comprehensively considers the impact of aerodynamic heating outside the cabin, air natural convection in the cabin and forced convection on the cabin thermal environment, thereby effectively solving the problem of determination of temperature field distribution of the cabin of the carrier rocket in the flight phase in the atmospheric layer.