Cancer metastasis is a complex dynamic cascade with multiple steps, and is influenced by various kinds of biochemical and biophysical factors in the microenvironment. The stiffness of the substrate is considered one of the most important factors for appropriate physiological function in numerous contexts. The extracellular matrix (ECM) around the cell is a material with viscoelasticity, the role of which in the cascade of events of cancer metastasis is poorly understood. This study establishes a 3D metastasis research model to investigate the influence of ECM viscoelasticity on the cascade of events of cancer metastasis in a suitable in vitro microenvironment. In the model, tumor cells and ECM can be precisely patterned in microfluidic channels, affording cancer cell an in vivo-like pathophysiologic three-dimensional (3D) microenvironments. The viscoelasticity of collagen gel was controlled via collagen gel concentration, measured by rheometer. The effects of viscoelasticity on the viability, cytoskeleton, invasion, and migration of hepatocellular carcinoma (HepG2) cells were investigated. our results reveal that the viscoelasticity of collagen gel increased with increasing concentration of collagen. The viability decreased with increasing viscoelasticity. The cytoskeleton seems denser in collagen gel with high viscoelasticity. The migration rate decreased with increasing viscoelasticity. These results suggest that the microfluidic device fabricated as a metastasis model could provide an in vivo-like pathophysiologic microenvironment for cancer cells to monitor the response of cancer cells to changes in their environments in real-time. We conclude that the viscoelasticity of collagen gel, mainly the elasticity, plays a role in the viability, cytoskeleton, capacity, and rates of invasion and migration of HepG2 cells.