The invention discloses a particulate loading amount calculating method for a particulate filter. The calculating method comprises the steps of judging the Peclet number of a particulate settled layer, calculating the micro-parameter of the particulate settled layer, backwards reasoning the thickness and the loading amount of the particulate settled layer according to the pressure drop, and calculating the particulate loading saturation. A device comprises an ECU, a pressure sensor, a temperature sensor, an oxygen sensor, an air mass flow rate sensor and the like. According to the purpose of the invention, by considering that under the different working conditions of an engine, the particulate deposited microstructures are different, the loading amount of particulates in the particulate filter is calculated through a theoretic pressure drop model, and accordingly, the regeneration opportunity is precisely controlled; and meanwhile, the particulate loading saturation is calculated to represent the loading degree of the particulate filter, and the positive effects on particulate filter service life prolonging and renewable energy consumption reducing are well achieved.