The bistable feature of unabsorbed pump in pump-bypassed Yb-doped fiber (YDF) laser offers a possibility to pump the Er/Yb co-doped fiber (EYDF) in a bifurcated cavity. By this way, the lasing of the second lasing line is in a switching mode with that of 1040 nm lasing line. In this paper the wavelength-switchable lasing of 1040-nm and 1537-nm dual lines is investigated experimentally, and the results suggest that a switchable two-wavelength source could be accomplished efficiently by combining the bistable feature of Yb-doped fiber laser with the hybrid cavity configuration (pump-bypassed cavity plus the bifurcated cavity).