Abstract: Based on the damage phenomena, steel strain distribution, and force-deformation relationships observed during quasi-static experiments on reinforced concrete retainers, two typical failure patterns are identified; diagonal shear failure and horizontal shear failure. The rigid body rotation hypothesis is introduced to model the failure mechanism of the retainers, and dual independent strength contribution terms are suggested to represent the contributions from concrete and reinforcements. Two strength analytical models are established corresponding to the aforementioned two failure patterns. The two models are essentially the same but with distinct force diagrams. In the diagonal rigid body rotation model, the retainer strength comes from concrete, shear steel, horizontal tension steel, and horizontal side steel, whereas in the horizontal rigid body rotation model, the retainer strength comes from concrete and shear steel. In both models, basic parameters such as retainer size, material properties, and reinforcement amount are formulated, and the effects of loading position and reinforcement location are also taken into consideration. Error analysis shows that the two models give accurate and reliable predictions, which can provide practical reference for seismic design of retainers.