This article presents a Negative-pressure-powered U-trapper of Spheroid Assembling System (NUSAS) and four unique features are addressed: (1) Negative pressure powered medium driving, (2) HepG2/3T3 gradient distribution and mixing co-culture, (3) Cell trapping effect via gravity force and liquid flow co-activation, and (4) Large area of U trapper array. The development of in vitro liver device benefits liver toxicology and metabolism.[1,2] However, due to the complexity of human liver tissue, it has been rarely discussed what kind of hepatocyte to fibroblast ratio has nearest performance to a real liver tissue. Here, we culture liver/fibroblast cells with gradient ratio as multicellular assembling spheroids simultaneously to find this ratio. These results based on our efficient approaches give us meaningful foundations to investigate biomedical character of 3D HepG2/3T3 artificial tissue in different mixing cell conditions.