Display omitted •Improve the precision of non-contact stress measurement for mistuned blisk.•The novel method depends on the data gotten by Blade Tip Timing.•The precision can be increased at least 4% compared with the direct method.•The maximum relative error is 0.5% in numerical simulation and 12% in experiment. It is crucially important to monitor the dynamic stress of turbomachinery rotating blades for residual fatigue life prediction and health management, especially for the aircraft engine mistuned blisk. This paper presents an improved non-contact dynamic stress measurement method based on fundamental mistuning model (FMM). The precision of the dynamic stress measurement can be improved at least 4% by the novel method compared with the direct calculation method, and the total stress measurement error is less than 12%. In this paper, only the tuned finite element model, mistuned natural frequency and vibration displacements at each blade tip are needed. The mistuned dynamic stress is expressed in the mistuned modal coordinate system with the stress coordinate base and coordinate values. The numerical and experimental investigations were carried out. This study provides a roadmap to measure the dynamic stress of rotating mistuned blisk, with a strong application potential in the stress online monitoring for the industrial turbomachinery with a blade tip timing (BTT) monitoring system.