Device and method for preparing special slow-release fertilizer for crops

The invention relates to a preparation device and method of a slow release fertilizer special for crops, the preparation device comprises a shell, and further comprises a screening assembly arranged in the shell and used for screening out powder in granular basic fertilizer, a fan is arranged on the discharging side of the screening assembly, and a cover plate is arranged above the screening assembly and the fan; and the conveying belt is arranged below the discharging side of the screening assembly. Powder mixed in granular basic fertilizer is screened out through the screening assembly, the conveying belt receives and conveys the granular basic fertilizer poured down after screening, and airflow generated by rotation of the fan drives the powder to move towards the inner wall of the cover plate and adhere to the inner wall of the cover plate. A transverse plate and a shifting plate are pushed to move through rotation of an eccentric part I, so that granular basic fertilizer is continuously turned over, coat