Disclosed are a method and an apparatus for testing residual stress in coatings. The method includes: obtaining elastic modulus of a coating and a substrate of a target object; obtaining a temperature during the coating preparation of the target object; obtaining a cross-sectional area of the coating and a cross-sectional area of the substrate of the target object; obtaining a thermal expansion coefficient of the coating and a thermal expansion coefficient of the substrate of the target object; and calculating the coating residual stress σc of the target object by the following formula: σ c = ( S s S c ) · [ 1 - ( E s ⁢ S s E c ⁢ S c + α c α s ) / ( 1 + E s ⁢ S s E c ⁢ S c ) ] · E s ⁢ α s ⁢ Δ ⁢ ⁢ T c , wherein, Sc is the cross-section area of the coating, Ss is the cross-section area of the substrate, Ec is the elastic modulus of the coating, Es is the elastic modulus of the substrate, αc is the thermal expansion coefficient of the coating, αs is the thermal expansion coefficient of the substrate, and ΔTc is the temperature during the coating preparation.