Principles and factors affecting the efficiency of different methods for extracting available K from six potassium-bearing minerals were investigated in current study. These methods included salt solutions, cation exchange resins and NaBPh4 methods. The results showed that the effectiveness of K extraction from minerals by salts was mainly dependent on the ion type, concentration and pH value of the solution. Different salts had different preferential effect on K release from various minerals. NH4+ saturation led to the collapse of the interlayer structure of the minerals and restrained non-exchangeable K (NEK) release remarkably. The effectiveness of K extraction by cation exchange resins method was mainly related to the ion type used to saturated resin beads and somewhat to the shaking speed used. Comparing with Ca2+, H+ and Na+ saturated resin had stronger K exchanging capacity from solution. For eliminating the effect of film mass transfer resistance on K exchange by resins, a shaking speed higher than 120 r/min was recommended. The solubility product constant of KBPh4 was 2.40×10-8 (25℃) based on the data got in current study. Without NaCl, NaBPh4 concentration was the main factor affecting the effectiveness of K extraction from minerals. According to the mechanism and efficiency of different methods, ammonium salts are suitable for evaluating K availability in soils with high content of exchangeable K. However, non-ammonium salts which can extract a small portion of NEK under long time extraction procedure, is superior to ammonium acetate to evaluate K availability in soils containing NEK available to crop. Cation exchange resins which can also extract NEK are more suitable for in situ research of soil K movement, but the procedure is relatively tedious. Different portion of NEK could be efficiently extracted with the NaBPh4 method via modification of the K extracting power of the method. The NaBPh4 method is assumed to be a good method for evaluation of available K in various soils in future.