In this paper, we proposed and experimentally demonstrated an 8-channel O-band DFB laser array with highly uniform 400-GHz spacing and high output power for the optical I/O technology. The grating phase is precisely controlled, and an equivalent π phase shift is implemented in the laser cavity via the reconstruction equivalent chirp (REC) technique. Anti-reflection (AR) and high-reflection (HR) films are coated on the front and rear facets, respectively, to enhance output power. The equivalent π phase shift is strategically placed near the HR film facet to improve the yield of the single longitudinal mode. Operating with a 400 GHz wavelength spacing, the proposed DFB laser array meets the CW-WDM MSA specifications. The proposed DFB laser array is flip-chip bonded to a thin-film circuit with an AlN submount to reduce thermal resistance and enhance the output power. Compared to the p-side-up structure, the flip-chip bonding design significantly reduces junction temperature by 28% and increases maximum output power by approximately 20%. This design effectively lowers the thermal resistance of the chip and enhances its heat dissipation properties. At a bias current of 110 mA, the laser demonstrates wavelength deviations below 1.579 GHz and side-mode suppression ratios above 50 dB. The far-field divergence is measured at 25.8° × 30.1°, and the Lorentzian linewidth is 3.28 MHz. Increasing the bias current to 250 mA results in a laser output power exceeding 80 mW. Furthermore, the relative intensity noise (RIN) for all 8 channels is below -135.3 dB/Hz. The proposed flip-chip bonded 8-channel high-power DFB laser array demonstrates uniform wavelength spacing, high output power, and stable single longitudinal mode performance, making it a promising candidate for multiple wavelength laser sources in optical I/O technology.