A wristwatch, as a timing instrument, is always an indispensable commodity for people in their daily work and life. A wristwatch usually comprises: a time indicating component which is the kernel component of the wristwatch and is used for indicating time; a watch case for housing and protecting the time indicating component; a watch band for fixing the wristwatch to people's wrist and for adorning purpose. With the development of science and technology, people integrate other devices into the wristwatch to make full use of the wristwatch as a portable commodity. For example, in a patent application numbered “CN01 104642.2” and titled “a telephone wristwatch with a SIM card”, a wristwatch combined with communication technology is disclosed. But, there is still no portable wristwatch combined with computer technology up to now, despite of the wide spreading and continuous development of computer technology. On the other hand, to meet the desires of data exchange, various types of mobile memory devices are present in the market, such as mobile hard disks, portable memory devices with a USB connectors, etc. Data exchange can be realized between computers by utilizing these products. For example, data from one computer is downloaded and stored to a portable memory device with a USB connector quickly, and then the data in the memory device is transmitted to another computer through the USB connector. Generally, the data stored in these products with Flash Memory can be downloaded rapidly and stored for a long time, for some instance, more than ten years. However, the mobile hard disk is not portable, and the existing portable memory device with a USB connector has to be equipped with a long cable, which connects with the USB connector of the product on its one end, and with the USB port of the computer on the other end. It often causes a lot of inconvenience since a consumer has to always carry the cable with him, and data transmission and storage becomes impossible if the cable is lost. Therefore, it is desirable to develop a portable memory device integrated with daily commodity like a wristwatch, so that the USB product needs not to be carried additionally.