To develop new anti-tumour Pt(ii) agents, we designed and synthesized five Pt(ii) complexes. These Pt(ii) complexes were modified benzene rings of 2-hydroxybenzylidene with a hydrocarbyl or halogen group. The five Pt(ii) complexes possessed remarkable cytotoxicity against tumour cells in vitro. In particular, we investigated chemotherapeutic mechanisms of the complexes against A549cisR cells. The Pt(ii) complexes could bind to and cleave DNA, while also inducing arrest of the cell cycle in S phase, leading to down-regulation of the levels of cyclin-dependent kinases and cyclin and up-regulation of the expression of p21. The selected complex, C3, changed the mitochondrial membrane potential and induced apoptosis. C3 also inhibited the expression of the c-myc gene and downstream proteins, thereby inhibiting telomerase activity.