Two new alkaloids (1 and 2), named 1,7-dimethoxy-2 '-prenyl-1 ',9-dihydropyrrolo-carbazole (1) and 1,7-dimethoxy-4 ',5 '-dimethylcyclopenta-carbazole-1 ',3 '-dione (2), along with thirteen known alkaloids (3-15) were isolated by means of silica gel, sephadex LH-20, and semi-preparative HPLC from the CHCl3 extraction of Corydalis decumbens for the first time. Their structures were determined by NMR, MS, IR, UV, and related references. Compounds (1-15) were evaluated for their antidepressant activities by measuring inhibition of monoamine neurotransmitter reuptake in vitro. Among them, compounds 1, 2, 4, and 6 showed certain antidepressant activities.