A particle-based electrochemical biosensor was developed by integrating soft magnetic material, NiFe, with interdigitated array (IDA) electrodes. The NiFe strips were embedded beneath the IDA electrodes and acted as magnetic traps to collect the enzyme labeled paramagnetic particles from a microchannel flow of particle suspension. The IDA electrodes, which overlap on top of the NiFe strips, are designed to detect in close proximity the enzyme product that is produced from the particle surface. The sensors were fabricated in such a way that the particles were positioned among IDA electrodes without blocking the active electrode surface. The theoretical prediction of the sensor response is presented. It is expected that both sensitivity and limit of detection of the biosensor would be improved significantly.