Reflection characteristics of a novel fiber loop mirror (FLM), which is formed by inserting a fiber polarization controller (PC) into the loop, are investigated. Based on the equivalent optical-path analysis, a theoretical model for the FLM is presented. The reflection characteristics of the FLM are then simulated in detail with the model. Our simulation results show that, by varying the PC working conditions, i.e. the fast axis orientation or the intensity of the birefringence induced by the PC, the refrectivity of the FLM may be continuously tuned between 0 and 1. The spectral characteristic of reflectivity of the FLM is wide and flattened, limited only by the operating bandwidth of the optical fiber coupler used. Moreover, the reflection characteristics of the FLM are further investigated experimentally. The experimental results also show that by varying the working conditions of the PC, the reflectivity of the FLM may actually be continuously adjusted between its maximum and minimum values,which were measured to be 93% and 2%, respectively. The experimentally determined dependence of the fast axis orientation and intensity of the birefringence induced by the PC on the inclination angle of the three rigid discs with respect to the level of the PC verified the results of theoretical simulations.