The invention relates to an ultrasonic detection device for bolts. The device comprises a bolt clamping part and a probe clamping part. The probe clamping part is located above the bolt clamping part, and the two can be connected together by relative rotation. The bolt clamping part includes a circular chassis, the center of the circular chassis has a clearing hole. The clearing hole wall of the circular chassis is uniformly equipped with three locking screws along the peripheral direction. The circular chassis is also provided with a locking screw linkage mechanism. The probe clamping part comprises a hollow shell, the lower end of the shell is an opening, the opening end is rotatably connected to the upper part of the circular chassis, a radial adjustment screw rod transversely passes through two opposite sides of the shell, and the shell is internally provided with a probe clamp assembly. The invention also provides a detection method. The device and the method provided by the invention have the characteristics of good reliability and repeatability, can realize full record of test data, and reduce operation steps.