The invention provides a device and a method for testing the flexibility of a carbon fiber. The device for testing the flexibility of the carbon fiber comprises a totally-enclosed test box, wherein the test box is provided with a weight used for correcting the distort of a carbon fiber to be measured; a test platform is arranged on the left side in the test box; a scale used for adjusting the height up and down is arranged on the right side in the test box; a graduated scale is arranged on the scale. After the carbon fiber to be measured is repeatedly measured by using the device for testing the flexibility of the carbon fiber, the average measurement value is test datum of the flexibility of the carbon fiber. According to the device and the method for testing the flexibility of the carbon fiber, errors caused by visual inspection or handfeel of different testing personnel can be avoided, and an effective test method is provided for evaluating the flexibility of the carbon fiber. According to the device and the method for testing the flexibility of the carbon fiber, the flexibility of the carbon fiber can be quantitatively tested, and exact reference data are provided for evaluating the process applicability of the carbon fiber.