Method for judging content of chromium element in plastic by internal standard-standard sample superposed laser-induced breakdown spectroscopy

The invention discloses a method for determining chromium content in plastic based on internal standard-standard sample superposition laser-induced breakdown spectroscopy. According to the invention, a beam of pulse laser is divided into two beams which respectively act on a plastic standard sample covered by a plastic film standard sample and a detected plastic sample covered by the plastic film standard sample, the contents of Yb in the two plastic film standard samples are the same, and the characteristic spectral signal intensity ratios of Yb and Cr are in direct proportion; and performing conversion according to the characteristic spectrum signal intensity of Yb in the plastic film standard sample to obtain a characteristic spectrum signal intensity conversion value of Cr in the detected sample, and comparing the characteristic spectrum signal intensity conversion value with the characteristic spectrum signal intensity value of Cr in the plastic standard sample so as to judge the relationship between the