The invention provides a volume fracturing horizontal well pressure dynamic analyzing method and device. The volume fracturing horizontal well pressure dynamic analyzing method comprises the steps that a double-medium model corresponding to a to-be-analyzed well section is built through a fractal theory; according to the double-medium model, a pressure dynamic model of the to-be-analyzed well section is built through a fractional order calculus method; and according to the pressure dynamic model, pressure dynamic analysis is conducted on the to-be-analyzed well section. By utilizing all embodiments in the invention, through the fractal theory and the fractional order calculus method, the pressure dynamic model of the to-be-analyzed well section is built, the to-be-analyzed well section canbe solved through a semi analytical method, the solution of the pressure dynamic model can be rapidly and accurately obtained, and the accurate data foundation is provided for subsequent pressure dynamic analysis of the to-be-analyzed well section. The accuracy of the analyzed results is improved while the calculated amount of horizontal well pressure dynamic analysis is reduced.