The invention provides an initial rainwater removal device. The device takes spectroscopical analysis as a determination means, is used for combined system overflow pollution control and water resource recycling, can be directly mounted in an inspection well and comprises a water quality online sampling detection unit, a main control unit and an automatic control circuit. The water quality onlinedetection unit performs sampling determination on incoming water by utilizing a sampling system; the main control unit performs analysis on spectral data and liquid level data and issues a related instruction; and the automatic control circuit comprises a UV254 signal transmission unit, an ultrasonic liquid level meter, a hydraulic gate and a hydraulic checkgate and is in charge of receiving an instruction issued by the main control unit and regulating and controlling opening and closing states and an opening degree of a valve. The device provided by the invention is high in automation degreeand quick in response, can timely and accurately remove combined system sewage on rainy days, controls combined system overflow pollution to the maximum extent and realizes recycling of a rainwater resource.