In order to improve the fatigue performance of new-type steel-concrete composite orthotropic deck, fatigue test and numerical investigation were conducted to evaluate the fatigue performance of its rib-to-crossbeam welded joints. First of all, a double-rib theoretical model joined with hinges was presented to analyze shear behavior of large size rib due to torsion and bending of orthotropic deck. Then the stress and cracking in the concrete slab and steel details were measured and analyzed in the full-scale specimen. The theoretical results showed a good correlation with the observed stress results. The test results indicated that the fatigue stress of rib-to-deck joints decreased significantly with overlaying concrete, namely the risk of fatigue cracking reduces. The proposed composite orthotropic deck is recommended as a new solution to the steel deck cracking.