A new method for the determination of inclusions of boron and titanium in medium and low alloy steel has been reported in this paper. The technique of original position statistic distribution analysis based on statistic analysis of more than ten thousands primary optical signals is applied in the present method. It is found that the abnormal high intensities in emission lines of boron and titanium occurred when a discharge volatilizes the material containing inclusions of boron and titanium. Some statistic algorithms are developed to distinguish the signals related to nonmetallic inclusions from the signals generated from soluble boron and titanium. Furthermore, mathematical models based on the relationship between the frequency of abnormal sparks and content of inclusions is put forward in this paper to count the contents of inclusions of boron and titanium. The results calculated by the present model have good coincidence with the value obtained by chemical methods. The present method has been applied to the determination of the contents of inclusions of boron and titanium in some certified reference materials and some real medium and low alloy steel samples.