The invention discloses an opening-and-closing-degree-adjustable grappler. The grappler comprises a hook body, a grappler body, an adjusting mechanism, a pedal and a top buckle, wherein an antiskid layer is arranged at the front end of the hook body; a toothed bar is arranged at the tail end of the hook body; the tail end of the hook body is connected with one end of the grappler body through the adjusting mechanism; the pedal and the top buckle are fixedly arranged at the other end of the grappler body; an antiskid layer is arranged on the top buckle; the pedal is provided with a buckle belt; the adjusting mechanism comprises a connecting body, an adjusting knob, a rack and a gear; the rack and the gear are arranged at the tail end of the grappler body; the gear is arranged in the connecting body; the gear is adapted to the rack; the adjusting knob is coaxially connected with the gear. The opening-and-closing-degree-adjustable grappler is safe, reliable, convenient and flexible in use, the hook body and the grappler body can be quickly adjusted to form the width of a buckling periphery, the grappler is simple in operation and suitable for operation by one hand of a worker, the danger that the worker departs a pole when the worker climbs the pole can be effectively prevented due to the fact that an anti-rotation clamping pin is additionally arranged, and the working safety of the worker who climbs the pole is greatly guaranteed.