Abstract: Enhancing the bioleaching of low-grade phosphorite ore by mixed strains composed of Acidithiobacillus ferrooxidans,Acidithiobacillus thiooxidans and Leptospirillum ferrooxidans was studied.The results showed that it was not suitable to bioleach this phosphorite ore due to its low content of S,adding pyrite as enhancement to the leaching solution was recommended and the effects of process parameters such as bacteria variety,mass ratio of phosphorite ore to pyrite and initial mass fraction of Fe²⁺ on the bioleaching rate of phosphorus were investigated.A higher leaching recovery was achieved with the acclimated mixed strains.The optimal leaching parameters were determined as follows:the initial Fe²⁺ mass fraction of 9 g·L^-1 and the mass ratio of phosphorite to pyrite by 1:2.5.Under the optimal condition,the phosphorus recovery rate reached up to 95% within 20 d.