Ultra-low speed gearbox for crawler tractor

The invention relates to an ultra-low speed gearbox for a crawler tractor. The gearbox comprises a power input shaft and a four-six gear shaft, wherein an intermediate gear and a transmission gear are coaxially and fixedly arranged on the four-six gear shaft respectively; the intermediate gear is in engaged connection with an input gear of the power input shaft; a sliding shift gear arranged on the four-six gear shaft consists of a master gear and a slave gear integrally, and is coaxially arranged on the four-six gear shaft in a sliding mode through a sliding bearing; a secondary gearbox is fixedly arranged on the lower part of the gearbox; a decelerating shaft is arranged parallelly in the same direction of the four-six gear shaft in the secondary gearbox; and a decelerating driven gear and a decelerating driving gear are fixedly arranged on the decelerating shaft. The gearbox is simple in whole structure, scientific and reasonable transmission design and reliable in mechanical operation, effectively improves the working range, working efficiency and working quality of the crawler tractor, reduces energy consumption, realizes ultra-low speed function of the crawler tractor, greatly facilitates the development and improvement of agricultural machinery, and effectively saves manual labor and material resources.