The performance of an erbium-doped fiber ring laser based intra-cavity absorption gas sensor was evaluated with performance enhanced techniques. A multi-line wavelength sweep technique and a weighted averaging technique were proposed for better gas detection. By selecting appropriate system parameters，6 strong absorption lines near 1 530 nm of C2H2 were obtained with good spectrum resolution in one scanning period. One group with higher absorption coefficients was used for relatively low gas concentration detection and the other with lower absorption coefficients was used for relatively high gas concentration. Both the groups can be used for medium gas concentration detection. For various concentration cases，by choosing proper absorption lines and performing weighted averaging, detection accuracy can be obtained over an extended detection range. The minimum detection limit could be very low after optimization.