Using the daily maximum and minimum temperature dataset from 128 stations from 1960 to 2004 inNorthwest China, daily extreme high temperature (EHT) and extreme low temperature (ELT) thresholds were deter-mined by centesimal method for different stations at first, then yearly EHT and ELT events were counted up in differ-ent stations, and the characteristics of their spatio-temporal distribution were diagnosed at last. The study drew follow-ing conclusions: 1) The consistent anomaly distribution characteristic was the most important mode of the EHT andELT events in Northwest China. 2) The spatial distribution of the EHT and ELT events can be divided into fivesub-regions, namely, the north of Qinghai and west of Gansu, the north of Xinjiang, the south of Xinjiang, the east ofNorthwest China and the south of Qinghai. 3) The EHT events showed remarkable increasing trend in all of fivesub-regions, but only in the north of Qinghai and west of Gansu area, sudden change phenomenon occurred; the ELTevents showed decreasing trend in all of five sub-regions, and sudden change phenomenon occurred in NorthwestChina except for south of Qinghai. 4) In all of five sub-regions the EHT events showed remarkable 12-14yr period os-cillation, and the ELT event showed significant 13-15yr and 7-Syr period oscillation. 5) The EHT and ELT eventsdisplayed remarkable positive and negative responses to regional warming of Northwest China respectively.