Two new chromeno[3,2-c]pyridine alkaloids, 9-acetyl-7-methoxy-3-methyl-10H-chromeno[3,2-c]pyridin- 10-one (1) and 8-acetyl-7-methoxy-3-methyl-10H-chromeno[3,2-c]pyridin-10-one (2), were isolated from the whole plants of Thalictrum scabrifolium. Their structures were determined by means of HR-ESI-MS and extensive 1D and 2D NMR spectroscopic studies. Compounds 1 and 2 were tested for their antibacterial activity. The results showed that both compounds showed high antibacterial activity against 12 microbial strains isolated from the saliva of smokers.