To solve the problems associated with titanium alloy joining, this study examines the fatigue behavior of TA1 titanium alloy single-lap clinched joints. Dynamic response data and strength degradation tests were conducted to track the variations in natural frequency and residual strength with increasing fatigue cycles. The cyclic ratio was utilized to quantify the correlation between natural frequency changes and strength degradation, establishing a model to predict the joint’s fatigue life and damage progression. Based on the natural frequency change and strength degradation index model, the service state calculation model of TA1 titanium alloy clinched joints is established to realize the prediction of residual strength and residual life of the joints. The results show that the natural frequency change and the strength degradation show similarity in the damage stage, which corresponds to the different degradation stages of the joint under fatigue service. The joint service state calculation model realizes the prediction of the current remaining strength and remaining life of the joint by collecting the instantaneous natural frequency, and the model is found to have good accuracy through experimental verification.