Abstract: A new type of low carbon bainite spring steel was prepared and its mechanical properties were tested. The results show that its mechanical properties were very poor. The reasons for the poor mechanical properties were analyzed by means of chemical composition analysis, hardness test, metallographic examination, inclusion composition analysis and so on. The results show that there were many inclusions and casting defects in the low carbon bainite spring steel, which caused the uneven composition of the steel and seriously destroy the continuity of the metal matrix, resulted in the poor mechanical properties of the low carbon bainite spring steel.