The invention relates to an epitaxial preparation method of a base region slowly-varying silicon-carbide-doped film. The method comprises steps as follows: (1) a silicon carbide substrate is placed in a reaction chamber of silicon carbide CVD (chemical vapor deposition) equipment, and the reaction chamber is pumped to be vacuum; (2) H2 is introduced into the reaction chamber until the gas pressure of the reaction chamber reaches 100 mbar, the gas pressure of the reaction chamber is kept to be constant, the flow of H2 is gradually increased to 60 L/min, and gas is introduced into the reaction chamber continuously; (3) a high-frequency coil induction heater RF is started, the power of the heater is increased gradually, and in-situ etching is performed when the temperature of the reaction chamber is gradually increased to 1,400 DEG C; (4) when the temperature of the reaction chamber is in a range of 1,580-1,600 DEG C, the temperature and the pressure are kept to be constant, the flow of an Al source is set, C3H8 and SiH4 are introduced into the reaction chamber, and a P type slowly-varying silicon-carbide-doped film epitaxial layer is grown by adjusting the flow of C3H8 and SiH4 which are introduced into the reaction chamber in a slowly-varying manner. According to the method, the silicon carbide CVD equipment is utilized, the silicon carbide epitaxial layer with the controllable longitudinal doping concentration gradient is prepared, and the requirement for preparation of the gradient low-doped epitaxial layer is met.