Two new protoberberine alkaloids, 2,3,9,10-dimethylenedioxy-8-oxoprotoberberine (1) and 2,3,9,10-dimethylenedioxy-1,8-dihydroxyprotoberberine (2), together with nine known isoquinoline-type alkaloids were isolated from the roots of Thalictrum delavayi. Their structures were elucidated by spectral methods. Among these compounds, pseudoprotopine showed competitive inhibition activity by DA receptor binding assay (D-1) in vitro. The competitive inhibitions were 87.5% (10(-4) M) and 15.6% (10(-6) M), respectively.