Andrographolide-lipoic acid conjugate (AL-1) is a new in-house synthesized chemical entity, which was derived by covalently linking andrographolide with lipoic acid. However, its anti-cancer effect and cytotoxic mechanism remains unknown. In this study, we found that AL-1 could significantly inhibit cell viability of human leukemia K562 cells by inducing G2/M arrest and apoptosis in a dose-dependent manner. Thirty-one AL-1-regulated protein alterations were identified by proteomics analysis. Gene ontology and ingenuity pathway analysis revealed that a cluster of proteins of oxidative redox state and apoptotic cell death-related proteins, such as PRDX2, PRDX3, PRDX6, TXNRD1, and GLRX3, were regulated by AL-1. Functional studies confirmed that AL-1 induced apoptosis of K562 cells through a ROS-dependent mechanism, and anti-oxidant, N-acetyl-l-cysteine, could completely block AL-1-induced cytotoxicity, implicating that ROS generation played a vital role in AL-1 cytotoxicity. Accumulated ROS resulted in oxidative DNA damage and subsequent G2/M arrest and mitochondrial-mediated apoptosis. The current work reveals that a novel andrographolide derivative AL-1 exerts its anticancer cytotoxicity through a ROS-dependent DNA damage and mitochondrial-mediated apoptosis mechanism.