The invention relates to a microbubble generating and gas dissolving device for sewage treatment. The device comprises a horizontal gas dissolving tank, a bubble partition filler, a water inflow pipe, a water outflow pipe, a gas inflow pipe group, a gas release pipe and a pollutant discharge pipe, wherein the water inflow pipe is horizontally inserted or verticality inserted from the upper part or lower part of one end outside the horizontal gas dissolving tank body and is connected with a single or row-type water spray pipe horizontally arranged in the top space of the horizontal gas dissolving tank, and water spray nozzles are arranged on the lower half-periphery of the water spray pipe; the water outflow pipe is horizontally inserted or verticality inserted from the upper part or lowerpart of the other end outside the horizontal gas dissolving tank body and is connected with a single or row-type water collecting pipe horizontally arranged in the lower space at the bottom of the horizontal gas dissolving tank, and water outflow holes are formed on the lower half-periphery of the water collecting pipe; two groups of single or row-type gas release pipes are horizontally arranged in the upper space of the water collecting pipe, the gas release pipe groups are in parallel connection with a gas introduction pipe outside the horizontal gas dissolving tank body, and micro-scale gas release holes are formed on the periphery of the gas release pipes; the bubble partition filler is filled between the gas release pipe groups and the water spray pipe; and the structure has high flotation efficiency.