The aim of this research is to design Three-Dimensional Magnetic Sensor, and uses the readout circuit to amplify sensor’s output voltage. The purpose of this paper is uses Three-Dimensional Magnetic Sensor to sense terrestrial magnetism. While integrate all circuit in one chip, reducing the Sensor volume and production cost. In this paper we present Three-Dimensional Magnetic Sensor consist of one Z-axis magnetic sensor and one XY-axis magnetic sensor, then use readout circuit and low pass filter to amplify and filter, finally the instrument amplifier output the voltage result. The measure result Sensor output voltage range is from 1 mV to 5 mV, and magnetic field range is from 0 Guess to 40 Guess, sensitivity is 9 V⁄AT to 19 V⁄AT.