The main factor of rubber fatigue was stress field. But the way is not sensitive in many cases. To clarify which factors were the main for predict the locations of fatigue crack, we analyzed the factors of stress field and strain field of rubber joint, and relations between the factors and the locations of fatigue crack, using 3D FE simulation. The result showed stress concentration was not sensitive to predict the locations of fatigue crack. The locations are close to strain concentration of rubber joint. In this paper we propose the approach of using strain concentration to predict the fatigue crack locations for rubber joint. This result is significant for the rubber joint design and the study of fatigue strength theoretic.