An antenna system is provided. The antenna system has a system grounding unit, a metal frame and a main board. The metal frame is spaced apart from the system grounding unit to form a clearance zone. The metal frame is a first radiator. The antenna system further has a second radiator, a switch, a capacitor and a main matching circuit. The second radiator is located in the clearance zone. The main board has a feeding point. The metal frame has a first connecting part and a second connecting part. An end of the capacitor is connected to the second radiator, and another end of the capacitor is connected to the main matching circuit. The second radiator is connected to the main board via the switch.