Recently, along with the booming of research and production of CMOS Integrated Bio-sensing System, selective assembly of organic nano-particles on the on-chip electrodes, which serves for specific bio-sensing and detection purposes, is in high demand in areas like biological analysis and detection, DNA probing and surveying systems and etc. In this paper, a fully integrated bio-circuit targeting at electrical selective assembly of charged nano-particles is proposed and designed in SMIC 0.18 μm CMOS mixed signal process. The proposed circuit integrates the 16 pixels of 19 μm × 19 μm electrode array, counter electrode, potentiostat circuit, digital decoding circuit, as well as control logics on a single chip, and provides a rail-to-rail range of assembling voltage, a potential resolution of 8 bit, and a maximal assembling current up to 459 μA, biased at a current of 1 μA. Meanwhile, a novel electrode-reuse scheme is also proposed to further simplify the architecture and save chip area as well, without degrading the functionalities. Experimental results from on-chip selective assembly of 50 nm polystyrene nano-particles are included and discussed to verify the feasibility of the proposed circuits.