The present invention provides a method and a device for quantitative analysis of an element, and belongs to the technical field of spectral analysis. The method is as follows: acquiring the concentration and spectral line intensity of at least two target spectral lines of a to-be-detected element of each sample in a calibration sample set, calculating weighted spectral line intensity of the to-be-detected element of each sample according to preset weighting coefficient of each target spectral line and the spectral line intensity of each target spectral line of each sample, finally performing linear fitting according to the concentration of the to-be-detected element of each sample and the calculated weighted spectral line intensity of the to-be-detected element of each sample to determine a calibration curve for quantitative analysis of the to-be-detected element. The method for quantitative analysis of the element takes multiple spectral lines for weighting processing, accurate analysis caused by the reason that when a single spectral line is used in quantitative analysis, spectral line fluctuation can be caused by plasma fluctuation or external interference can be avoided, and the accuracy and stability of system analysis can be effectively improved.