A new hybrid optical bistability device which comprises a fiber Mach-Zehnder interferometer and two fiber couplers is proposed. In the device, the fiber Mach-Zehnder interferometer is used as light intensity modulator and the fiber couplers are used to construct on optoelectronic feedback loop. The theory of bistability has been analyzed and illustrated. At last, the optical bistability is fulfilled by changing the input optical power in the experiment. The device can be used as a fiber laser power stabilizer when it works at the stable status and as an optical switch or optical router when it works at the switching status.