The invention discloses a process for removing heavy metal ions in wastewater through a pressurized dissolved air flotation method and a device thereof, and belongs to the field of environmental engineering governance. The process comprises the steps: firstly introducing calcium hydroxide into the wastewater, making calcium hydroxide neutralize acidic ions in the wastewater, then introducing sodium oleate to make the formed precipitate hydrophobizated, and then flocculating particles; generating micro-bubbles by the pressurized dissolved air method, discharging the saturation dissolved air water generated after pressurization to the flocculated wastewater, and carrying out flotation; and finally collecting and processing the scum obtained by flotation. The process belongs to a pressurized dissolved air flotation purifying process, is concise in process and convenient to operate, and can be continuously operated.