Phosphorus deficiency has become one of the abiotic stresses that hinder the enhancement of crop yield. It has become one of the hot spots in crop science to screen out low phosphorus tolerance resources and carry out crop breeding for low phosphorus tolerance, and it is particularly important to monitor the phosphorus content in plants timely and effectively. In this paper, the content of phosphorus in the tissues of fresh and young leaves and roots of foxtail millet were determined by molybdenum antimony anti-colorimetric method before and after improvement. It was found that the phosphorus content measured by the modified molybdenum antimony anti-colorimetric method has a good linear relationship with the colorimetric absorbance in a certain range. The linear equation was y=1.060 3x-0.010 3, and the linear correlation coefficient was 0.998 1. Using the method for foxtail millet fresh tender leaf, mature young root, leaf, root, fresh young ear, mature stalks and those tissues which was frozen by liquid nitrogen, and the foxtail millet seeds, the phosphorus content from these different millet crop tissues, and their phosphorus content under different phosphorus concentration treatments (0.005, 0.250 mmol/L) were determined. It is proved that this method has good sensitivity and precision, and the standard deviation measured by this method is small, within the range of 0~0.015 8. The relative standard deviation (RSD) ranges from 0% to 1.81%. The detection limit ranges from 0 to 0.047 4 μg/mL, with good repeatability. The method can also be used to effectively screen foxtail millet varieties with different phosphorus absorption efficiency. Modified molybdenum-antimony anti-colorimetric method has agood linearity, low standard deviation and ideal precision, which is suitable for the determination of low concentration phosphorus in plants, and can provide a basis and reference for the determination of total phosphorus in different foxtail millet materials.