Abstract: Surface tension driven self-assembly has been demonstrated to be a promising method for mass production of highly 3-D MEMS structures. However, factors and their mechanisms affecting the self-assembly precision of the hingeless structures are still barely understood. This study addresses and analyzes some of the factors, including the inherent instability of the hingeless structures, scale effect and the deformations of the limiter structure which limits the self-assembly precision of hingeless structures. An energy based model, verified by the experimental results, was introduced to evaluate the adverse effect of each factor on the precision. This precision study can serve as an optimum guideline for the designs of self-assembly MEMS microstructures and allow the creation of high precise MEMS applications.