The invention provides a nuclear power reactor bolt inner hole bidirectional ultrasonic inspection probe, which comprises an installation bracket and a probe, wherein the installation bracket comprises a support bracket and a support pipe; the support bracket is also elastically connected with a probe bracket; two sides of the upper surface of the probe bracket are respectively provided with symmetrical inclined planes; the probe is fixed on the inclined planes; and the lower surface of the probe bracket is sunken inwards to have two symmetrically arranged inner concave surfaces which point tothe upper surface of the probe bracket and intersect to form a sharp part; the support pipe is fixed with an expansion sleeve which can be expanded and supported between the outer wall of the supportpipe and a bolt inner hole. The nuclear power reactor bolt inner hole bidirectional ultrasonic inspection probe has reasonable structural design, can effectively improve the stability of the probe when entering the bolt inner hole for exploration, maintains the concentricity of the probe and the bolt inner hole, and improves the exploration quality and the exploration precision.