Lactic acid is a metabolic product of human physiological activity. It is of great importance in the diagnosis and treatment of diseases and scientific sports management. It is necessary to build a lactate biosensor that can realize rapid and accurate detection of lactic acid. Graphene supported platinum nanoparticles (GPNs) were prepared by the redox reaction between graphene oxide, chloroplatinic acid and ethylene glycol. Pt nanoparticles were highly dispersed on the graphene, and the surface platinum content of the prepared GPNs was as high as 28%. The GPNs showed excellent electrochemical performance compared to graphene modified electrodes or platinum modified electrodes. An enzymatic lactic acid biosensor (ELB) was prepared by immobilizing lactate oxidase (LOx) on the GPNs modified glassy carbon electrode. The response current of the sensor at +0.4 V in the presence of lactic acid showed a wide linear relationship in the range of 0-1.0 mM, and the limit of detection (LOD) was calculated to be 8.0 mu M according to S/N = 3. The ELB was free from common interfering species, and exhibited excellent stability. From the 1st day to the 15th day, the response signal lost less than 2%. (C) The Author(s) 2018. Published by ECS.