In recent years, with the rapid development of multi- collector inductively coupled plasma- mass spectrometry (MC- ICP- MS), the analytical precision of potassium (K) isotopes has been greatly improved, which in turn has promoted their development as potential geochemical tracers in processes involving continental weathering, crust- mantle interaction, and so on. Until now, the cumbersome and time- consuming process of sample pretreatments and the poor analytical accuracy caused by argon hydrides interference are still the biggest obstacles to the wide application of K isotopes. After completely dissolving the samples with hydrochloric acid, nitric acid, and hydrofluoric acid, purification of K from major matrix was performed on a customized quartz ion exchange column packed with ~2. 7 mL of AG50W- X8 cation exchange resin (BioRad TM，200~400 mesh) using 0. 5 mol/L HNO3 as the eluent. This one- step procedure can effectively separate K from Li, Na, Ti, Mg, Mn, Al and Ca, except for Cr, in most of the geological samples. To find the appropriate method for high- precision stable K isotopic measurements, for minimizing the ArH+ yield and improving the stability of the instrument, three methods were compared here (the high- resolution mode, high- resolution mode with continuous acquisition measurement run mode, and the low- resolution mode with a method designed to eliminate ArH+ interference). The low- resolution mode has the advantages of low cost, high stability, and high precision (long- term precision at about 0. 08‰ for our laboratory). When used to measure the K isotopic composition of a series of international geological reference materials, the results are consistent with previous values within analytical precision, indicating the reliability of this method. The K isotopic composition of a set of Chinese national rock standard materials is determined here. The measured values of K isotopes can provide a reference for the data comparison between different laboratories in future.