Lots of studies have investigated the shear contribution of the fiber-reinforced polymer of reinforced concrete beams with externally bonded fiber-reinforced polymer (FRP). In this paper, based on more than 200 collected experimental results of reinforced concrete beams shear strengthened with U-jacketing fiber-reinforced polymer composites, four existing design guidelines on the fiber-reinforced polymer shear contribution of strengthened reinforced concrete beams are compared in terms of the effect of the shear span-to-effective depth ratio, beam size, and stirrup ratio. These three influence factors are found to play significant roles in the prediction accuracy of different design guidelines. This paper, therefore, proposes an advanced shear strength model, which considers the effect of shear span-to-effective depth ratio, beam size, and stirrup ratio. The proposed model can provide better predictions of fiber-reinforced polymer shear contribution.