A cloud device, a terminal device, and an image classification system and method includes the terminal reading an image to be classified; transmitting an instruction of image classification to the cloud device; determining whether the instruction of image classification comprises an intermediate operation result of the first partial operation; performing the second partial operation to obtain an image classification result, when the instruction of image classification comprises intermediate operation result of the first partial operation; and transmitting the image classification result to the terminal device; performing the first partial operation to obtain the intermediate operation result, when the intermediate operation result is not contained in the instruction of image classification; transmitting the intermediate operation result to the terminal device; and performing the second partial operation to obtain an image classification result.