A tunable bi-directional optical add-drop multiplexer (Bi-OADM) based on fiber Bragg grating (FBG) is proposed and demonstrated. The center wavelength of the optical add-drop multiplexer (OADM) is tuned without chirp by using open and closed piezoelectric ceramic (PZT) separately. The tunable range can reach 6 nm, while the range of commercial eight wavelengths multiplexing system is 5.6 nm. The experiment shows a good reproducibility in the voltage load and unload curves when using open loop in small voltage and using closed loop in big voltage (more than 80 V). Employing optical switches and alternate-path switching scheme, the bi-directional transmission can make one-direction light path normally transmit when the other direction light path is fail in the ring network, which can greatly improve the reliability of OADM. The experimental results indicate that the tunable Bi-OADM shows a low insert loss (4 dB).