The invention relates to an adjustable-processing-height landscape garden road trimming device and a use method of the landscape garden road trimming device. The landscape garden road trimming device is used for carrying out chamfering trimming on the top edge of the outer side of curbstone (21), and comprises a machine frame (9), a walking wheel (92) and a walking pushing handle (91), wherein the walking wheel (92) is arranged at the lower end of the machine frame (9); the walking pushing handle (91) is arranged at the upper end of the machine frame (9); a sleeving member (101) matched with the machine frame to vertically slide is arranged in a position, above the walking wheel (92), of the machine frame (9); one side, near the curbstone (21), of the sleeving member (101) is fixedly provided with a transverse bearing rod (93); a guide wheel slide sleeve (951) and a trimming grinding wheel assembly slide sleeve (931) are sequentially and glidingly borne on the transverse bearing rod (93) from inside to outside; in addition, the cross section of the transverse bearing rod (93) is in a square shape, so that the guide wheel slide sleeve (951) and the trimming grinding wheel assembly slide sleeve (931) are prevented from rotating on the transverse bearing rod (93).