The invention relates to a nondestructive examination method for anchored bolt length and an examination device thereof, which belongs to nondestructive examination, and solves the problems of complex process and bulky apparatus of the prior examination method which is thus not suitable for field examination. The method comprises the following steps: firstly, taking a free bolt which is the same as the examined bolt and has a length of LO, selecting the impulse transmission frequency to be 2.25MHz, and analyzing the first edge echo of the free bolt; secondly, performing FFT analysis to each separated wave packet of the first edge echo of the free bolt, and obtaining the peak frequency of each separated wave packet of the edge echo and the arrival time thereof; thirdly, examining the anchored bolt according to the impulse transmission frequency set in step one, selecting the first edge echo of the anchored bolt, and obtaining the peak frequency of each separated wave packet of the edge echo of the anchored bolt and the arrival time thereof according to the processing in step two; fourthly, selecting data f1 and f2 which have the smallest frequency value difference and the corresponding arrival time T1 and T2; fifthly, calculating the length L of the anchored bolt according to the following formula.