A new type of micro amperometric sensing chip based on gold interdigitated microband array (Au-IDA) electrode for trace nitrate determination has been developed. The Au-IDA microelectrode is fabricated with micro-electro-mechanical systems technology. Three-dimensional (3D) nano-structured dendritic silver is electrochemically deposited on the Au-IDA microelectrode surface, which shows superior electrocatalysis property in facilitating nitrate reduction. The results show that the sensing chip has a sensitivity of 9.5 nA/mu mol/L, limit of detection of 10 mu mol/L, detection dynamic range of 10-1000 mu mol/L, and linear range of 25-1000 mu mol/L nitrate (R-2=0.9998). Interference analysis with 9 kinds of ions (NO2-, F-, PO43-, H2PO4-, SO42-, CO32-, NH4+, Na+ and K+) commonly found in surface water indicates that the proposed microchips have good selectivity to NO3-. It is noteworthy that the proposed 3D nano-structured dendritic silver modified Au-IDA microelectrode could be used for nitrate analysis in neutral media which is important for field and real-time monitoring nitrate ions in natural water.