Recycled aggregate concrete (RAC) composite slabs with closed-profiled steel decking not only take full advantages of composite slabs, but also realize the reuse of waste concrete. In this work, flexural tests on this novel composite slabs with different coarse recycled aggregate (CRA) replacement rates were carried out. The failure modes, load-displacement curves and strain development at the mid-span were investigated. Afterwards, a finite element model of the composite slabs was established, and the effects of CRA replacement rate, clear span and thickness of steel decking on the flexural capacity were analyzed. Finally, based on the experimental results and finite element parameter analysis, a calculation formula for the flexural capacity of the new composite slab under positive flexural conditions was proposed. Results indicated that the degree of upward shift of the neutral axis decreases with increasing CRA replacement rate during the whole bending process. The composite slabs with different CRA replacement rates mainly exhibits bending failure. The flexural capacity of recycled concrete composite slabs is 6.6% to 8.9% lower than that of normal concrete slabs. A simplified calculation formula that considers partial plastic development of the steel section and the influence of recycled aggregate replacement rate can effectively predict the bending capacity of the composite slabs.