The invention discloses a system for obtaining a clear target image under rain and fog weather conditions. The system comprises an image collection device used for collecting an image; a lens protection cover covered on the outer side of a lens of the image collection device, wherein an interdigital transducer is arranged on the inner side of the lens protection cover, and the interdigital transducer converts electric energy into surface acoustic waves to drive droplets dropping onto the outer side of the lens protection cover to move downwards along the lens protection cover; an image processing device connected with the image collection device for processing the image collected by the image collection device; and an image monitoring device connected with the image processing device for receiving the image processed by the image processing device. The system can obtain the clear target image under the rain and fog weather conditions, so as to improve the image quality and reliability of image monitoring. Correspondingly, the invention further discloses a method for obtaining the clear target image under the rain and fog weather conditions.