The graded composite materials were fabricated by direct inkjet printing of nano-electropolar mineral and nano-hydroxyapatite powders for the study of inhibiting function on streptococcus mutans, which is a primary pathogen for human dental caries. The electropolar mineral can be utilized in many fields due to its spontaneous permanent polarity and far infrared emission properties. In this study, the graded distribution of the streptococcus mutans on the surface of graded composite materials was investigated by energy dispersion spectrometry, and the mechanism of which is that the streptococcus mutans was remained in the culture of pH at about 8.5 self-adjustment induced by the electropolar mineral. This culture inhibits growth and acid production of streptococcus mutans. Therefore, this composite materials have inhibitory effects on streptococcus mutans, and can be used as a promising biomaterial for preventing human teeth from caries.