The present invention provides a fluorine-containing triazolopyridine represented by formula (I) and a racemate, R-stereoisomer, S-stereoisomer, pharmaceutically acceptable salt, or mixture thereof. The triazolopyridine can be used as a positive allosteric modulator of an mGluR2, and is highly selective in activating the mGluR2, exerting no activation or very limited activation of other homologous metabotropic glutamate receptor. The triazolopyridine can thus be used to prepare a product for treating an mGluR2-related disease, such as a central nervous system disease or neurological disease.