In this paper, we provide a class of surfaces called ϵ-isothermic surface in the pseudo-Euclidean 3-space and introduce pseudo-Calapso equation. We prove that for each surface, can associate two solutions to particular, Calapso, Zoomeron Davey-Stewartson III equations. sequence, classify Dupin having distinct principal curvatures explicit coordinates such surfaces. As application theory, obtain...