The present invention discloses a tri-frequency duplexer circuit and multi-frequency duplexer circuit. The tri-frequency duplexer circuit comprises a microstrip line circuit, two first mushrooms, two second mushrooms and two third mushrooms. The microstrip line circuit comprises a first Input/Output (I/O) port, a second I/O port, a third I/O port and a fourth I/O port. The two first mushrooms are respectively disposed at transmission line paths between the first I/O port and the second I/O port and between the first I/O port and the third I/O port. The two second mushrooms are respectively disposed at transmission line paths between the first I/O port and the second I/O port and between the first I/O port and the fourth I/O port. The two third mushrooms are respectively disposed at transmission line paths between the first I/O port and the third I/O port and between the first I/O port and the fourth I/O port.