Taking some uranium ore as bioleaching object,the growth state of bacteria and the change regularity of pH,Eh,concentration of Fe~(2 ) in leaching system were investigated by experiments.It was identified that the steady descent of pH value and Fe~(2 ) concentration,continuous raise of Eh value in lixivium can be respectively regarded as the signs that thiobacillus thiooxidans and thiobacillus ferrooxidans well grow and are adapted to uranium ore.