Several years ago,together with Fan and Jarvis,we constructed a Gromov-Witten type theory in Landau-Ginzburg setting.It has applications in the geometry/integrable system correspondence and Landau-Ginzburg/Calabi-Yau correspondence.Since then,it has generated quite a bit activities in geometry and physics.Recently,we generalized our theory to a more general class of model in physics called gauged linear sigma model.It has a variety of applications such as geometric LG/CY correspondence.In the talk,we will present the construction and its wall crossing phenomenon.The wall-crossing formula provides a geometric way to approach LG/CY correspondence.