The invention discloses a chemotherapy puncture positioning device capable of adjusting a positioning distance, solves the problems of unstable positioning and non-adjustable positioning distance of apuncture needle in the prior art, and has the effects that the positioning distance can be adjusted according to different puncture depths, the positioning is stable, and a contact area between a puncture position and an external environment is reduced. According to the technical scheme, the device comprises a transverse adjusting mechanism capable of clamping or loosening the puncture needle, the transverse adjusting mechanism is connected with a fixing mechanism through a plurality of longitudinal telescopic mechanisms which are evenly arranged at intervals, and the fixing mechanism is connected with a protection device; the transverse adjusting mechanism is adjusted to enable the longitudinal telescopic mechanism to extend or retract to change the positioning distance; wherein the transverse adjusting mechanism comprises a first positioning ring and a driving ring which are arranged together in a sleeved mode, the driving ring can rotate relative to the first positioning ring, anda transverse telescopic mechanism is arranged on the inner side of the first positioning ring.