The invention discloses an adjustable well testing top sheave, and relates to the technical field of oil-gas field equipment. The adjustable well testing top sheave comprises an arc-shaped wire pressing assembly, a sheave assembly and a sheave bracket assembly, wherein the sheave bracket assembly comprises a mounting seat, an adjusting screw nut, an adjusting screw, a sheave bracket, a rotating lock sleeve and a bracket lock sleeve, one end of the sheave bracket is used for mounting the sheave assembly, and the other end is inserted into the adjusting screw and rotates relative to the adjusting screw through a sheave radial bearing; and the rotating lock sleeve is arranged on the adjusting screw and the adjusting screw nut in a sleeving manner and used for adjusting locking of the adjusting screw and the adjusting screw nut. The adjustable well testing top sheave is simple in structure and reasonable in design, and can adjust height of the sheave to separate instruments captured at a wellhead smoothly.