The invention discloses a waste gas treatment device and a treatment method and is applied to waste gas treatment in a chemical engineering process. The method combines a biological method and a photocatalysis method, is low in mating device cost and simple to operate, is applicable to waste gas treatment of various emission amounts and concentrations, intensifies the waste gas removal rate and solves defects that a common waste gas treatment method is low in treatment capacity, large in energy consumption, low in removal rate and serious in secondary pollution. The waste gas treatment methodmainly comprises the following steps: performing primary biological purification on a waste gas by using a microbial suspension in a reaction chamber A; and performing secondary photocatalytic purification on the waste gas in a reaction chamber B by using an ultraviolet lamp and a photocatalyst TiO2. The waste gas treatment device comprises a reaction chamber A, a heat exchange sleeve, a gas distributor A, a defoamer, a flange, a reaction chamber B, a gas distributor B, an ultraviolet lamp, a catalyst carrier and the like.