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In order to explore the influence of initial strain on the photo-oxidation aging process of HDPE sheath, the actual strain value of HDPE sheath was calculated based on the design method and the production process of parallel steel wire suspender. The initial strain of HDPE specimen was applied by fixture, and xenon arc lamp accelerated aging test of HDPE were carried out. The results show that after 5000 h xenon arc lamp accelerated aging, the tensile strength, yield strength and secant modulus of the elastic stage of the specimen decrease by 11.19%, 9.15% and 40% respectively. During the aging process, there is no obvious increase or decrease in the elongation at break.There is a critical time in the aging process, when the aging time exceeds the critical time, the yield elongation of HDPE specimen will increase sharply; When the aging time is less than the critical time, the tensile properties of the specimens are basically unchanged with the increase of the initial strain; When the aging time is greater than the critical time, with the increase of initial strain, the tensile strength of the specimen decreases gradually, while the yield strength and secant modulus increase gradually. The critical time increases with the increase of initial strain. In addition, based on the experimental results, the prediction model of HDPE strength and secant modulus is established. The results of this paper lay a foundation for the prediction of the remaining service life of HDPE sheath, which can provide a theoretical basis for the durability design of suspension bridge cable system. • The tensile properties of HDPE sheath for parallel wire suspender after photo-oxidative aging is explored. • The characteristics of elastic stage, strain softening stage, necking stage and orientation hardening stage are analyzed. • With the increase of aging time, the tensile and yield strength and secant modulus in the elastic stage decrease. • When the aging time exceeds a critical time, the yield elongation of the specimen suddenly rises. [ABSTRACT FROM AUTHOR]