Mesenchymal stem cells are ideal seed cell alternatives for articular cartilage tissue engineering, and the methods of the expansion of seed cells need to be improved. The mechanical factors play a significant role in the process of articular cartilage development and regeneration. The aim of this study was to improve the chondrogenic differentiation of mesenchymal stem cells and to expand seed cells for articular cartilage tissue engineering based on mechanical factors. Rabbit bone mesenchymal stem cells were subjected to cyclic dynamic square wave tensile mechanical loading using the FX-4000 tension system. The viscoelasticity of cells was investigated using the micropipette aspiration technique combined with the Kelvin standard linear viscoelastic solid model. The cell chondrogenic phenotype was assessed by detecting characteristic chondrocyte biomarkers; the expression of the GAG and TGF-β1 was analyzed by ELISA, and the expression of the Col2α1 and Sox9 gene was analyzed by RT-PCR. The results show that proper tensile mechanical stimulation improves the viscoelasticity and chondrogenic phenotype of mesenchymal stem cells such that it is similar to that of chondrocytes. These results suggest that viscoelasticity is a specific marker of chondrogenic differentiation and that proper mechanical stimulation culture methods can be used to expand seed cells and improve the chondrogenic phenotype for articular cartilage tissue engineering.