Wind turbine blades(WTBs) are prone to damage or failure under the influence of factors such as long-term operation and harsh environments. Damage identification of WTBs was studied using vibration transmissibility functions. The theory of damage identification based on vibration transmissibility function was introduced, and the method of using signal coherence to determine the frequency range for calculating the damage index of transmissibility was proposed. Using the Workbench platform, numerical simulations of WTBs were conducted to analyze single and multiple damages at various locations and severity levels. The effects of frequency band selection and sensor placement on damage detection capabilities were evaluated. Experimental modal tests on blade models verified the feasibility and effectiveness of the proposed damage identification methodology. The results show that this method can effectively identify, locate, and assess WTBs' damage. The use of frequency bands with high signal coherence, identified based on coherence analysis, resulted in enhanced detection of localized damage.