In the process of the high speed pay-off of the optical fiber cables, there are some problems unsolved such as testing the broken fibers or cables, monitoring the working states of the pay-off, and so on. In this paper, in order to solve these problems, a kind of dynamic testing technology to test the bending losses and the bending parameters of optical fiber pay-off cables based on the dual-wavelength, at the high pay-off speed, is proposed. Using the dual-wavelength method, the distribution of bending radius and bending length near the stripping points of the fibers on the optical fiber cable steel can be inversed by the difference of the bending loss index. On the other hand, a kind of dynamic dual-wavelength testing device is designed and developed, which is of broad band and high sensitivity and can obtain the periodic signals of the cable loss index with the changing of strong bending in real time. Besides, the static and dynamic calibration devices are designed, and the relationship between the two calibration methods is also established. Furthermore, the relationship between the curvature radius and the strong bending losses when the curvature radius is less than 6mm and the relationship between the bending length and the loss is studied experimentally. The results show that it has fast time response, strong anti-interference ability and high sensibility. There is obvious difference of the bending states between the scanning interval and the retrace interval, and the loss in the retrace interval increases greatly more than in the scanning interval. It is important to note that the minimum curvature radius of the strong bending cable is about 0.5mm at the speed of 200m/s. Our work will be beneficial to analysis the process and the mechanism of the fault of the fiber broking, as well as the fiber communication, fiber sensor, and so on.