This paper reported synergistic bimetallic AuCu/TiO2 catalysts for selective oxidation of 1,2-propanediol to lactic acid under very mild conditions (T<90 degrees C, 1MPa O-2). The addition of Cu to monometallic Au/TiO2 catalyst leads to a twofold activity enhancement for Au catalysts (TOF: 11894h(-1)) with good selectivity towards lactic acid (S>92%). Surface characterization reveals that while AuCu forms alloy structure with larger particle size based on TEM images, strong interaction between Au and Cu species is critical for performance enhancement. According to experimental studies on the influence of 1,2-propanediol and NaOH concentration on reaction rates, it is highly possible that 1,2-propanediol is reacted following single-site Langmuir-Hinshelwood mechanism while NaOH acts as a promoter and may block surface sites under relatively higher concentration.