The invention discloses correction method and device of instrument drifts during X-ray fluorescent quantitative detection. The method comprises the following steps of: arranging a reference mechanism controlled by an instrument between an X-ray tube and a measuring sample box; arranging a reference sample formed by pressing according to metallic elements to be measured on the reference mechanism; and measuring the reference sample by using an X-ray fluorescence analyzer to obtain the pulse counting rate of the reference sample and use the pulse counting rate as an original target intensity value. When the X-ray fluorescence analyzer is operated for measuring, the counting rate of the reference sample needs to be measured before measuring an ore pulp sample each time, and the specific value of the counting rate and the original target intensity of the reference sample is used as a standardized coefficient; and the pulse counting rate of the ore pulp sample measured each time is corrected by utilizing the calculated standardized coefficient to obtain a standard pulse counting rate of on-line ore pulp measurement. The invention can compensate performance index drafts brought for a long time or a short time of the instrument in real time and improve the stability and the measuring precision index of the instrument.