An image processing system and an imaging device are provided. The image processing system includes a circuit board, an ambient light sensor, a light guide, a camera sensor and a camera lens. The ambient light sensor is integrated on the circuit board. An output end of the light guide is connected to the ambient light sensor to guide light to a detecting part of the ambient light sensor. The camera sensor is integrated on the circuit board. The camera lens is connected to the camera sensor. In the present disclosure, light guide is optically coupled with the ambient light sensor, such that a field of view of the ambient light sensor can be controlled to enhance color performance. Further, the light guide can provide spatial selectivity for the ambient light sensor while improving system integration and minimizing impact on appearance of the imaging device.