LHAASO has been built up and operated for one year. Many ultra-high energy gamma ray sources have been revealed. Sources have been investigated in depth such as the Crab nebula with a discovery of an extreme electron accelerator in side the nebula. Spatial extension with complexity seem to be the common feature of the UHE sources, To search for more specific features about particle acceleration, an improved resolution better than LHAASO is indeed required. LACT is a plan to enhance the resolution to the level of IACTs and simultaneously take the advantages from the muon detector array in LHAASO. The goal is to reach the similar sensitivity of LHAASO for UHE sources and unveil the acceleration mechanism for PeV particles.