The invention relates to a saliva streptococcus urase antibody, wherein the antibody is used for resisting an UreC interest protein, and a amino acid sequence of the UreC interest protein is represented as SEQ ID NO.5. The saliva streptococcus urase antibody has advantages of that: the saliva streptococcus urase antibody prepared in the invention can directly detect urase in an oral cavity, or is used for preparing kit for detecting the saliva streptococcus urase. The saliva streptococcus urase antibody is used for qualitatively, semi-quantitatively or quantitatively detecting the saliva streptococcus urase in dental plaque or saliva, wherein, compared to culture and identification of cariogenic bacteria, the detection method is more accurate, simpler and rapider; the saliva streptococcus urase antibody is used for directly detecting urase expression of a recombination bacterial strain containing a saliva streptococcus urase gene, wherein, compared with the detection of prior metabolites, the method is more visual and has scientific; and the saliva streptococcus urase antibody is used for detecting the urase in the oral cavity, wherein the method is further a method for determining cause of disease and serious degree of a bad breath patient.