A reflection rate detection device and reflection rate detection method for a liquid crystal panel are provided by embodiments of the present application. A sphere of the liquid crystal panel is a hollow sphere, and an inner wall of the sphere is uniformly sprayed with diffuse reflection materials. The sphere is provided with a window hole, and the window hole corresponds to the liquid crystal panel. The emitting light source is disposed on the sphere, the emitting light source is configured to emit light, and emitted light enters the liquid crystal panel. The receiver is configured to receive reflection energy of the liquid crystal panel. A reflection rate of a large-area liquid crystal panel can be detected by the present application.