A system of detecting magnetic field comprises a magnetic impedance element surrounded by a detection coil, a stimulus unit that generates pulse signal of programmable rise/fall time to drive the magnetic impedance element, and a signal detection module that detects signal on the detection coil, wherein the signal detection module includes a buffer unit having adjustable bandwidth for shaping output signal of the detection coil, a signal amplify unit that includes a sample and hold circuit and a chopping programmable gain amplifier to amplify buffered signal from the buffer unit, a signal processing unit that processes amplified signal from the signal amplify unit by applying a selectable algorithm to output detection result, and a control unit that connects the signal processing unit to generate control parameters of the stimulus unit, the buffer unit, the signal amplify unit, and the signal processing unit.