In order to improve the quality of inductively coupled plasma-atomic emission spectrum and reduce the detection limit of analysis, the influence of potassium additives into water samples on water samples’ spectral intensity and signal-to-background ratio was studied. The excitation temperature and electron density of plasma were measured through multi-line slope and the Stark broadening method. The results demonstrated that the plasma spectral intensity intensity increases to a various degree after adding potassium additives into the sample solution. When the content of the potassium is 1.0 g·L-1, the spectral lines intensity of element Al, Cr, Cu, Mn, Ni and Zn was increased by 8.62%, 32.29%, 108.45%, 6.06%, 64.98% and 54.99% respectively, the spectral signal-background ratio increased by about 7.90%, 30.95%, 104.60%, 5.21%, 66.00% and 52.82%, respectively. Under the conditions of the content of potassium is 1.0 g·L-1 in the sample, the plasma excitation temperature increased by about 239.69 K than that without additive, and the electron density increased by about 4.99×1011 cm-3. It is thus clear that potassium additives can improve the quality of inductively coupled plasma-atomic emission spectrum.