A new metal detector was designed, using LDC1000 digital inductance sensor and self-made coil as the metal detection sensor, based on eddy current principle. When the metal near the coil, caused by the mutual inductance, the LC oscillation circuit’s frequency changed, and the changed frequency could be converted to the digital output data. Furthermore, the data could be sent to STM32 for process and display, through the SPI interface. When the test value exceed threshold value, it could cause sound and light alarm. The test metal could detect 0.6 mm diameter of thin wire, and it might be used to food processing, security check and other fields. If equipped with Bluetooth and wireless communication, it might be used for the web of things security work.