Mehlich3 (M3) method can simultaneously determine the contents of soil available P, K, Ca, Mg, Al, Fe, Zn, Mn and Cu, and is feasible for calcareous, andosol and highly weathered soils. However, it is hard to get NH₄NO₃ used in M3 method due to its explosibility, therefore, it is necessary to find other substances to replace NH₄NO₃. In this paper, M3 method was modified by using indifferent-electrolyte ammonium chloride (NH₄Cl) to replace NH₄NO₃ (NH₄Cl-M3 method) to determine available elements in 30 topsoils. Pearson correlation analysis showed available P and K contents in the tested 30 topsoils determined by the two methods were significantly correlated, with determination coefficients (R²) of 0.99 (P=2.31×10^-55, n=60) and 0.98 (P=1.52×10^-49, n=60), respectively. Meanwhile, significant correlations were also found for available Ca, Mg, Al, Fe, Zn, Mn and Cu contents determined by the two methods, with R² values of 0.98, 1.00, 0.99, 0.96, 0.99, 0.95 and 0.94, respectively. Bray-P and Olsen-P of the above acid neutral and alkaline topsoils determined by the two methods were also significantly correlated, with R² values of 0.97 and 0.91 (P=1.42×10^-15 and 1.00×10^-21), respectively. Soil available P content determined by NH₄Cl-M3 method was significantly promoted than M3 method. Therefore, NH₄Cl-M3 method can be an alternative method to determine available P, K and other elements in calcareous and highly weathered soils as well as the amended soils.