The thirty-seven one meter class mirror segments which comprise the LAMOST primary mirror need precision support and cell to meet the demand of optics surface figure. Because true ZERODUR glass mirror has had the final design drawing that has been slight different from the former one, a modified sub-mirror finite element model and re-analysis have considered many new factors including the anti-drop groove, center blind hole and invar pad. At the same time, After a sub-cell prototype have been designed and manufactured, with a similar K9 glass mirror segment, the experiment of mirror figure testing is being conduct to verify sub-cell’s performance and modify some detail. The support truss of primary mirror also has new scheme. This paper introduces the sub-cell prototype experiment, analysis of sub-mirror and new support truss.