By using daily surface air temperature data of China′s 200 stations during 1951～1999,schemes of analyzing temperature extremum are designed. Firstly, a designed quality control procedure is performed for the daily data. Next, the thresholds of extremum are estimated in terms of the 95th and the 5th percentiles. Finally, spatial distribution of temperature extrema over China for 50 years is discussed and a new technique is proposed for detecting extreme events.