Abstract: This talk is devoted to study the ergodicity of smooth surface actions. We provide a sufficient condition for surface actions to be ergodic with respect to the Lebesgue measure. First, we address the main results obtained so far for the unit circle, as a main tool in higher dimensional. After that, by introducing the notion of flag manifold, we explain how rich minimality of sufficiently smooth action on the flag manifold may lead to the ergodicity of the initial action.