The invention discloses a crest height adjusting device of a crest welder. The crest height adjusting device of the crest welder is used for adjusting a crest nozzle. The crest nozzle is arranged in a trough formed by a bottom plate and side plates in an enclosed mode. The two ends of the crest nozzle are installed on the inner walls of the side plates in a sliding mode. Two lifting adjusting assemblies are symmetrically arranged at the bottom of the crest nozzle. Each lifting adjusting assembly comprises a rotary shaft. An eccentric wheel is installed on each rotary shaft. Each eccentric wheel abuts against a lifting adjusting plate. The two sides of each lifting adjusting plate are installed in guide rail troughs in a sliding mode. The guide rail troughs are fixedly installed on the side plates. The two ends of each rotary shaft penetrate through the side plates. Bearings are arranged in the positions where the rotary shafts penetrate out of the side plates. A handle is arranged at one end of each rotary shaft. Locking baffles are installed on the outer walls of the side plates. Locking screws are arranged on the locking baffles. After the locking screws are tightened, the ends of the locking screws abut against the rotary shafts, and the rotary shafts are fixedly locked.