A fully integrated CMOS bio-chip is designed in a SMIC 0.18μm CMOS mixed signal process and successfully integrated with a novel bio-nano-system.The proposed circuit integrates an array of 4×4 (16 pixels) of 19μm×19μm electrodes,a counter electrode,a current mode preamplifier circuit (CMPA),a digital decoding circuit,and control logics on a single chip.It provides a -1.6～1.6V range of assembly voltage,8bit potential resolution,and a current gain of 398dB with supply voltage of 1.8V.The offset and noise are smaller than 5.9nA and 25.3pArms,respectively.Experimental results from on-chip selective assembly of 30nm poly (ethylene glycol) (PEG) coated magnetic nano-particles (MNPs) targeted at biosensor applications are included and discussed to verify the feasibility of the proposed circuits.