Tunable wavelength converters are key components in intelligent all-optical network. In this paper, a novel scheme for tunable wavelength conversion based on semiconductor-fiber ring laser is proposed. Probe laser in the conventional scheme could be left out and self-started tunable wavelength conversion could be achieved. Theoretical model for this novel scheme is also established and the output characteristics are calculated. Experimental results show good agreement with theoretical results. In experimental study, 2.5Gb/s tunable XGM wavelengthconversion with 40nm tuning range was demonstrated. Experimental and theoretical studies show that this novel scheme is worthy of further investigation.