Abstract: Metal element contents in water samples are commonly determined by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). ICP-MS has a low detection limit and wide linear range, but has a high power, large gas consumption, and high cost. A rapid method for the determination of calcium ions in water samples was developed by using Microwave Plasma Torch (MPT)-Mass Spectrometry coupled with pneumatic nebulization. The effects of carrier gas flow rate and the support gas flow rate on calcium response signal were investigated. The detection limit of this method is 224.56 ng/L, relative standard deviations (RSDs) are 1.2%-9.8%, and recoveries range from 86.3% to 110.4%. This method avoids sample pretreatment, and has a short analysis time, good sensitivity and precision. This method provides a new approach for the determination of metal ions in environmental water and may be used for in situ analysis in the future.