A separable rack rail driving device having a monorail crane and suitable for a large slope, comprising a driving mechanism, a moving mechanism (5), a four-linkage mechanism, a connection mechanism, a meshing track plate (15), and a transition track plate (18). The driving mechanism comprises a drive motor (3), a meshing gear (2), a receiving rod (14), and a receiving support plate (13). The moving mechanism comprises a moving wheel (16), a clamping wheel (17), a housing, and a telescopic support rod (4). The four-linkage mechanism comprises a first rocker (12), a connecting rod (11), a second rocker (9), and an oil cylinder (10). When the monorail crane moves to the front of the slope, the oil cylinder drives the four-linkage mechanism in advance to feed the meshing gear into the transition track, and adjusts the four-linkage mechanism to a dead point state, such that the telescopic support rod is locked. After the device enters the slope, the meshing gear cooperates with the meshing track plate mounted on the slope to provide an auxiliary drive to the monorail crane moving uphill. The device overcomes the defect of insufficient power, and achieves the smooth and safe operation by means of the telescopic support rod and the dead point characteristics of the four-linkage mechanism.