NOVELTY - Preparation of composite microbial solution comprises mixing 5-15 mmol/kg nitrilotriacetic acid (NTA) chelating agent and 15 mmol/kg microbial solution, where bacterial solution is Pseudomonas stutzeri, Trichoderma reesei and Streptomyces griseoflavus at volume ratio of 1:1:1, number of colonies of Pseudomonas stutzeri and Streptomyces griseoflavus are 2.15 plus minus 0.03x 109/mL and 2.07 plus minus 0.07x 109/mL, and number of colonies of Trichoderma reesei spreads throughout flat plate.    USE - Method for preparing composite microbial bacteria solution used for strengthening Festuca arundinacea for repairing sewage irrigated soil heavy metal pollution (claimed).    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for strengthen of Festuca arundinacea comprising (A) taking Pseudomonas stutzeri, Trichoderma reesei and Streptomyces griseoflavus at volume ratio of 1:1:1 to prepare composite microbial solution, selecting nitrilotriacetic acid chelating agent, removing soil in collected roots, spreading on transparent plastic sheet, naturally drying for 2-3 days, and sieving; (B) adding 170 g test soil to polyethylene plastic cups as culture vessel, planting 0.5 g per cup tall fescue seed, plant growing for 15 days, adding composite microbial solution, plant growing for 25 days according to experimental design and corresponding concentration of NTA and bacteria, applying one-time to substrate surface, NTA treating after 10 days of harvesting for 35 days, growing turfgrass in laboratory, repositioning to ensure consistent illumination, where training room temperature is 17-31 degrees C and relative humidity is 38-60%, and cultivating with normal water supply, where concentrations of NTA are 5 mmol/kg, 10 mmol/kg, and 15 mmol/kg NTA and volume of microbial solution per concentration of NTA is 15 mL; and (C) sowing after 35 days, harvesting, repeatedly washing with deionized water, drying at 80 degrees C till constant weight, weighing, and detecting heavy metal content in digestion solution using TAS-990 atomic absorption spectrophotometer.