The invention relates to a plant fertilizer preparation assembly, belongs to the field of fertilizer preparation equipment, and provides a preparation assembly with advantages of delicate structure, convenient use and good stability and capable of rapidly and effectively converting domestic waste into a plant fertilizer with characteristics of no odor and easy use. According to the plant fertilizer preparation assembly, a preparation chamber is fixedly connected above a power chamber, a water storage chamber is fixedly connected to one side of the preparation chamber, the top portion of the preparation chamber is provided with a material inlet, the bottom portion of the preparation chamber is provided with a material outlet, the middle portion of the preparation chamber is communicated to the top portion of the water storage chamber, the top portion of the water storage chamber is provided with a water inlet, a stirring shaft is hinged in the preparation chamber, a piston is slidably connected in the water storage chamber, and a screw rod connected to the bottom portion of the water storage chamber through threads is arranged below the piston. According to the present invention, the plant fertilizer preparation assembly has characteristics of convenient use and no odor, the obtained fertilizer has sufficient nutrients and provides good irrigation effect for plants, and the whole output of the city garbage is reduced.