The paper deals with the climatic evolution since 22 ka BP in the Sêkazhig Lake area, Tibet. By studying a 670 cm thick section of hole SZK, a great deal of paleoenvironmental information has been obtained based on the microfossil record there. The section contains plenty of ostracod fossils, but their diversity is comparatively low. The fossils comprise 8 species in 4 genera and are grouped into 8 assemblages according to their distribution in strata. Their ecological features, combined with Useries and 14C dating, reveal that the lake area has undergone several great changes in climate and environment since nearly 22 ka BP: ① 22,060~15,070 a BP: the lake was shallow with low water temperatures, and the climate was cold and wet; ② 15,070~12,425 a B.P.: the climate got warm and wet, and the lake was enlarged and uplifted with rising water temperatures; ③ 12,425~10,010 a BP: the lake water table went down with low water temperatures again, and the climate was cold, and during the period of 11,585~10,920 a BP the climate became cold suddenly in response to the Younger Dryas cold event; ④ 10,010~7550 a BP: the climate was cold and wet, and the lake was enlarged again; ⑤ 7550~6730 a BP: the climate turned warm and wet, and the water temperatures kept rising; ⑥ 6730～5760 a BP: the water level lowered and the climate tended to be cold and dry; ⑦ 5760~4750 a BP: the climate kept cold and dry, and the lake was in the late stage of its development.