The invention relates to a clamp-on ammeter, and particularly relates to an adjustable clamp-on ammeter with a display. The clamp-on ammeter comprises a clamping head and a supporting rod, the clamping head comprises a left clamping tooth, a right clamping tooth, an ammeter and a clamping shaft, the supporting rod comprises a fixing device, a telescopic device, a display screen, a stay rope and arod body, the fixing device comprises a baffle plate and a linkage rod, one end of the baffle plate is connected with the right clamping tooth, the middle part of the linkage rod is hinged with the other end of the baffle plate, one end of the linkage rod is connected with the stay rope, the other end of the linkage rod is in abutment connection with the left clamping tooth, the telescopic deviceis arranged on the rod body, the tail end of the rod body is provided with a holding handle, the display screen is arranged on the rod body, the ammeter is connected with the display, the holding handle comprises a rotating shaft, a handle and a pulley, one end of the handle is hinged with the rod body, the rotating shaft is arranged at a part where one end of the handle is hinged with the rod body, the pulley is arranged on the handle, the stay rope is wound around the pulley, and the other end of the stay rope is arranged on the rotating shaft. The clamp-on ammeter has the beneficial effectsof more visual indication effect, higher reliability, simple and convenient use, adjustable length and the like.