This study presents a polyimide (PI) self-assembly technique for developing a 3-D surface-micromachined structure. The effects of geometric factors and curing temperatures of PI elastic joints on the lifting angles of such 3-D microstructures are investigated. Under the optimized curing condition , a maximum lifting angle of -weight polysilicon microplate is achieved utilizing a large thermal shrinkage force of a single PI joint. Before severe cross-linkage occurred (curing at ), the lifting angle of the thermally actuated 3-D microstructure is nearly in direct proportion to the length/width-thickness ratio of the PI joint (with linearity of 95.5%) and the difference between curing and room temperatures (with linearity of 92.3 to 97%). The PI-based self-assembly process is very suitable for mass production due to its high yield of fabrication (80 to 91.6%) and high compatibility with the present IC and MEMS manufacturing processes.