Many diorganotin complexes with various alkyl groups exhibit excellent in vitro anticancer activity. However, most diorganotin is the same alkyl group, and the asymmetric alkyl R group has been rarely reported. Hence, in this paper, twenty butylphenyl mixed dialkyltin arylformylhydrazone complexes have been synthesized by microwave “one-pot” reaction with arylformylhydrazine, substituted α-keto acid or its sodium salt and butylphenyltin dichloride. The crystal structures of nine complexes were determined, indicating that the complexes C1, C2, C11, C12, and C16 ∼ C19 possessed a central symmetric structure of a dinuclear Sn2O2 tetrahedral ring; while the complex C9 is a trinuclear tin-oxygen cluster with a 6-membered ring encased in a 12-membered macrocyclic structure. The inhibiting activity of complexes was tested against the human cell lines NCI-H460, MCF-7, HepG2, Huh-7 and HL-7702. Complex C2 demonstrated the optimal inhibitory effect on HepG2 cells, with an IC50 value of 0.82 ± 0.03 μM. Cellular biology experiments revealed that complex C2 could induce apoptosis and G2/M phase cell cycle arrest in HepG2 and Huh-7 cells. The complex also caused the collapse of the mitochondrial membrane potential and increased intracellular reactive oxygen species in HepG2 and Huh-7 cells. Western blot analysis further clarified that complex C2 could induce cell apoptosis through the mitochondrial pathway along with the release of reactive oxygen species.