Objective To research the effect of the location and depth of the lateral and penetrating cracks initiating at the leading or trailing edge of the disk blades on the frequency of the first-order flexural vibration of the blades. Methods The frequencies of normal blades in static and rotation were calculated through modeling according to the size and working condition, then the models for lateral and penetrating cracks were built by Booleans operation on the basis of normal blades to research the variation of frequencies affected by location and depth of the lateral and penetrating cracks and all the data was fitted. The modeling results were verified by the frequencies of the first-order flexural vibration of normal blades and those with different crack depth through DFT analysis of BTT signals. Results The results showed that the frequency decreased at first and then increased. The minimum frequency of 801. 16 Hz was got at the distance of 4. 23 mm. When the distance to the root was greater than 35 mm, the frequency became close to and then greater than the normal value, so the distance of 35 mm was set as the threshold of location. In addition, the frequency decreased with the increase of the crack depth, and the speed of changing kept increasing. The measurement errors of BTT signals with the results of FEM were 1. 9% , 2. 0% , 1. 5% and 0. 6% , respectively. Conclusion When cracks initiate at the leading or trailing edge within the location threshold, the frequencies of the first-order flexural vibration are lower than the normal val- ues, and the resonance region of first-order flexural vibration will expend so that the working condition needs to be monitored seriously. Meanwhile, the increase of the crack depth can improve the accuracy of BTT data.