Fluorine, potassium, sodium and sulfur in slag can be used for lubrication to prevent molten steel from adhering with the wall. Moreover, they can be also used to adjust the melting point and judge the source of defects. The certified reference materials of converter slag, blast furnace slag and electric furnace slag as well as the production sample of furnace slag after accurate determination were used to draw the calibration curve. The analysis method of fluorine, potassium, sodium and sulfur in slag by X-ray fluorescence spectrometry (XRF) with pressed powder pellet was established. The experimental conditions for sample preparation were obtained as follows: the ground sample passed through 200-mesh sieve (74 μm); the pressure of pressing machine was 20 MPa; the time of maintaining pressure was 30 s. One furnace slag sample was prepared and determined for 11 times according to the experimental method. The relative standard deviations (RSD, n=11) of determination results of testing elements were between 0.17% and 3.4%. The accuracy verification results showed that the determination results of proposed method were consistent with those obtained by other analysis method (high frequency combustion infrared absorption, inductively coupled plasma atomic emission spectrometry and ion selective potential method). The proposed method could meet the batch quantity and rapid analysis requirements of on-the-spot samples.