Rehmanniae Radix Praeparata is the processed products of the root of Rehmannia glutinosa. It has been used as a Traditional Chinese Medicine for thousands of years, and it has been found to possess widely pharmacological activities. In this study, three new 2,2′‐difurylketone derivatives (rehmanniaeketone A–C) and two new chromones [3,8‐dihydroxy‐2‐(2‐hydroxyethyl)chromone and 3,8‐dihydroxy‐2‐[(2‐O‐α‐D‐galactopyranosyloxy)ethyl]chromone] were isolated from the Rehmanniae Radix Praeparata. Furthermore all of the compounds were subjected to cytotoxic testing against the human lung carcinoma A549 cells. The cytotoxic results showed that rehmanniaeketone B and rehmanniaeketone C exhibited more stronger inhibition effects on the cell activity of A549 cells with the IC50 5.23 μM and 2.05 μM than other compounds. And 3,8‐dihydroxy‐2‐(2‐hydroxyethyl)chromone exhibited moderately inhibitory activity with the IC50 61 μM. Rehmanniaeketone A and 3,8‐dihydroxy‐2‐[(2‐O‐α‐D‐galactopyranosyloxy]chromone showed no inhibitory effects.