Abstract: K-feldspar, a ubiquitous mineral in igneous and metamorphic rocks, has long been used in K-Ar dating. However, a number of problems exist in K-Ar dating of K-feldspar. For example, K-feldspar usually yields younger ages than the co-existed minerals such as biotite. K-feldspar may also yield older ages in some cases. It is suggested that incomplete extraction of radiogenic argon from K-feldspar is one of the main reasons that leads to a younger age. Several solutions have been put forward to resolve the problem, but none of them has been successfully used in experiments. K-feldspar has low closure temperature （about 130 -150℃ ）, which can easily cause radiogenic argon lose; In addition, radiogenic argon from the wall rock as excess argon may also enter the K- feldspar. The low temperature K-feldspar （such as adularia ） shows capability to maintain various amounts of radiogenic argon which is related to their textures. The content of radiogenic argon in adularia is decreased with the increase of their triclinities. In summary, the applicabilities of K-feldspars from different geological environments are various in K-Ar dating. K-feldspars （such as micro cline and perthite） from intrusive rocks can not be used in K-Ar dating, while those （sanidine and anorthoclase） from extrusive rocks are very good ones, and the low temperature K-feldspars （adularia） can be used in dating conditionally