The invention discloses an intelligent preparation system and preparation method for synthesizing a quick-acting and slow-release integrated efficient ecological compound fertilizer through straw microbial fermentation. The system comprises a cutting unit, a fermentation unit, an intelligent control unit, a waste heat recovery unit, a press filtration unit, a grinding and crushing unit, a blending unit, a granulation and drying unit and a finished product sub-packaging unit, wherein the fermentation unit comprises a fermentation tank, a biogas recovery mechanism, a heating mechanism, a heat exchange mechanism, a sprinkling mechanism, an automatic feeding mechanism and a stirring mechanism. The method comprises the following steps: performing sealed fermentation on straws and animal feces; and performing water press filtration on a fermentation product, then performing high-temperature inactivation, adding an appropriate amount of inorganic quick-acting fertilizer and trace element fertilizer, rooting powder, a drought-resistant water retention agent and clay, mixing, and performing granulation and drying to obtain the compound fertilizer. By adopting the system and the method disclosed by the invention, fresh animal feces are used as a leaven which contains a lot of microorganism bacteria and digestive enzymes and can promote biological degradation and decomposition of the straws; and moreover, the animal feces are further fermented to be beneficial for opening unstable ester bonds in straw cellulose, accelerating the degradation of the straws and shortening the fermentation period.