Abstract: Ultra wide band （ＵＷＢ） accurate positioning system for underground personnel has been gradually popularized and used in coal mines. However, there is a lack of portable card reader, which can be used to search and rescue personnel in case of mining accidents and test positioning cards in daily life. Therefore, this paper studies and designs a mine portable card reader based on UWB technology and SDSTWR（ｓｙｍｍｅｔｒｉｃａｌ ｄｏｕｂｌｅ－ｓｉｄｅｄ ｔｗｏ ｗａｙ ｒａｎｇｉｎｇ） ranging algorithm. The card reader takes ARM master controller STM32F429 and UWB wireless transceiver chip DW1000 as the core, and realizes the information reading and accurate positioning of the positioning card. The test results show that the mobile card reader has an effective wireless ranging distance of 400 meters, the maximum static positioning error is no more than 0.3 meters, and the maximum concurrent identification number is 80 positioning cards, which can meet the requirements of coal mine and have important practical significance for carrying out scientific rescue after the disaster and daily system maintenance work.