The invention relates to a method for repairing lead-
chromium composite contaminated soil by combining 
humic acid and sudangrass. The method effectively solves the problem that 
humic acid reduces thebiological availability of 
heavy metals lead and 
chromium, relieves the poisons of the 
heavy metals lead and 
chromium to the sudangrass, creates conditions for the growth of sudangrass in moderately and severely contaminated areas, and improves the remediation efficiency of the sudangrass on the lead-chromium composite contaminated soil. 
Humic acid is uniformly scattered on the 
surface layer, withthe chromium content of 275.4 mg / kg or above and the lead content of 989.7 mg / kg or above, of the lead-chromium contaminated soil, the soil is plowed, raked and ridged, sudangrass seeds are sowed, watering is conducted once every 3-7 days in the 
plant growth process, management is conducted according to the 
normal growth requirement of the sudangrass, the sudangrass grows for 30 days, soil samples are collected and measured, the lead content of soil is smaller than or equal to 218 mg / kg, and the chromium content of soil is smaller than or equal to 95 mg / kg, so the national 
environmental standard requirements are met, and remediation of the lead-chromium contaminated soil is achieved. The method is simple, can effectively solve the problems of heavy 
metal combined 
pollution, difficult survival of plants and the like, and also has the advantages of soil improvement, 
fertility enhancement, 
crop growth promotion, low cost and environmental friendliness.