A narrow linewidth electro-optically tuned multi-channel interference (MCI) widely tunable semiconductor laser based on carrier injection is demonstrated in this paper. The MCI laser with a common phase section and a semiconductor optical amplifier (SOA) is packaged into a 16-pin butterfly box. The laser is characterized by a strategy: shifting the longitudinal mode and then aligning the reflection peak, which obtains a quasi-continuous tuning range over 48 nm. The corresponding side mode suppression ratios (SMSRs) are higher than 40 dB and frequency deviations from ITU-grid are less than ± 1 GHz. Threshold currents are less than 28 mA. Fiber coupled output powers are higher than 20 mW and power variations with fixed gain and SOA currents are less than 0.8 dB over the whole tuning range. Lorentzian linewidths are less than 320 kHz over the entire tuning range, which is one of the lowest results for monolithic widely tunable semiconductor lasers tuned by carrier injection. These results demonstrate the potential prospects of the MCI laser with carrier injection in the field of optical sensing and optical communications.