Based on a flexible twisted bilayer chiral metasurface sensor, utilizing terahertz timedomain spectroscopy technology, with chiral Lactic Acid(LA) enantiomers as the research subjects, a method for sensing the concentration of chiral substances and enantiomer recognition in the terahertz band is proposed. The results show that the Transmission Circular Dichroism(TCD) of the chiral metasurface sensor shifts with the increase of concentration, and the shift amounts are different for different chiral enantiomers. The highest detection sensitivity for Levorotatory Lactic Acid(L-LA) and Dextrorotatory Lactic Acid(D-LA) are 2.6 GHz/(mg/mL) and 1.9 GHz/(mg/mL), respectively, with a detection limit as low as 0.01 mg/mL. The great potential of the chiral metasurface sensor in LA sensing and chiral recognition provides an efficient, low-cost technical method for the sensitive detection of chiral enantiomers.