The invention discloses a sliding shifting gearbox for a spool type sprinkling machine. The sliding shifting gearbox comprises a gearbox body, an input shaft, a sliding shifting transmission shaft, transition transmission shafts and an output shaft; the sliding shifting transmission shaft is in a hollow tube structure, and comprises a gear supporting section and a sliding control section; the gear supporting section is matched and connected with a plurality of variable gears I having different transmission ratios in a sleeving manner; arc-shaped grooves are formed in inner holes of the variable gears I; a plurality of steel ball containing through holes are formed in the outer surfaces, corresponding to sleeving connection positions of the variable gears I, of the gear supporting section; steel balls are arranged in the steel ball containing through holes; a sliding shifting seat is arranged on the sliding control section in a sleeving connection manner, and is fixedly connected with a sliding shifting rod arranged in the hollow tube structure; and an ejection step is formed on the sliding shift rod. The sliding shifting gearbox for the spool type sprinkling machine is simple in structure and convenient to operate, wide speed regulating range can be realized, then high transmission efficiency with the sliding shifting gearbox being small-sized can be ensured, and the sliding shifting gearbox is particularly suitable for the small and middle-sized spool type sprinkling machines.