The invention discloses an image retrieval system and a retrieval method. The image retrieval system comprises a mobile device, wherein the mobile device at least comprises an image capturing unit, a processing unit and an image data server, the image capturing unit is provided with two cameras, the two cameras respectively capture an input image of an object at the same time, the processing unit is coupled with the image capturing unit and is used for obtaining a depth image according to the input image and determining a target object according to characteristic information of the depth image and the input image, the image data server is coupled with the processing unit, receives the target object, retrieves the corresponding target object and obtains retrieval result data, and in addition, the retrieval result data is transmitted to the mobile device. The image retrieval system and the retrieval method have the advantages that the problems that when the mobile device is applied to the image retrieval, the whole image needs to be transmitted to a remote server, and the server needs to carry out mass operation can be solved, the load and the processing time of the server are reduced, and the use affinity and the convenience are improved.