Abstract: In order to reasonably determine the fatigue strength of an orthotropic steel bridge deck, the fatigue test achievements at home and abroad are analyzed, and the effective fatigue test data is selected. Combined with fatigue cracking mechanism of typical details, fatigue strength categories (fatigue strength corresponding to 2 million cycles) for orthotropic steel bridge deck are proposed, which adapts to the anti-fatigue design and construction level of China. Research results show that: the fatigue strength of deck-to-rib detail is greatly influenced by the weld type, which belongs to Category 50 for fillet weld and Category 60 for partial penetration weld; for the rib-to-diaphragm detail, the fatigue strength of the welded toe of the diaphragm is Category 70, and that of the longitudinal rib web is Category 55; the fatigue strength of diaphragm cutout detail belongs to Category 70; the fatigue strength of rib-to-rib detail is closely relevant to the splice gap, which indicates that Category 40 is suitable for the splice gap less than 3 mm, Category 70 is suitable for the splice gap between 4 mm and 6 mm, and Category 100 is suitable for the splice gap between 8 mm and 12 mm. The fatigue strength of diaphragm weld toe in rib-to-diaphragm detail, of diaphragm cutout detail and of rib-to-rib detail is consistent with the categories in current JTG D64 specification of China. The fatigue strength of deck-to-rib detail and of rib wall weld toe in rib-to-diaphragm detail is lower than that of the categories in JTG D64 specification. When performing the anti-fatigue design or the fatigue assessment for orthotropic steel bridge decks, reasonable fatigue strength categories should be determined by the comprehensive factors of the detail structure, manufacture quality, actual service state and others.