A series of benzo[a]pyrano[2,3-c]phenazine derivatives with a wide range of substitutions at ring C of the benzophenazine were designed and synthesized using the one-pot, four-component domino reactions. The targeted compounds were evaluated for their antitumor activities against HCT116, MCF7, HepG2 and A549 cancer cell lines in vitro. The most active compound 6{1,2,1,9} featured the CN and p-dimethylamino phenyl substituents on γ-pyran structure on ring C. Significantly, compound 6{1,2,1,9} was found to have the highest growth inhibitory activity against the HepG2 cell line with IC50 values of 6.71 µM, which was 1.6-fold more potent than positive control anticancer drug Hydroxycamptothecine (HCPT). Furthermore, structure-activity relationship (SAR) studies on the substitutions at ring C were discussed in details.