The dissipative Kerr soliton microcomb provides a promising laser source for wavelength-division multiplexing (WDM) communication systems thanks to its compatibility with chip integration. However, the soliton microcomb commonly suffers from a low-power level due to the intrinsically limited energy conversion efficiency from the continuous-wave pump laser to ultra-short solitary pulses. Here, we exploit laser injection locking to amplify and equalize dissipative Kerr soliton comb lines, superior gain factor larger than 30 dB, and optical-signal-to-noise-ratio (OSNR) as high as 60 dB obtained experimentally, providing a potential pathway to constitute a high-power chip-integrated WDM laser source for optical communications.