Abstarct: Abstract In this study, the thermal post buckling behavior of a truncated composite conical shell with a lattice core and two composite laxyers is investigated. The shell is subjected to a uniform and linear temperature rise in thickness direction with simply supported boundary conditions at both ends. The shell is assumed to have an initial geometric imperfection and a lattice core composed of three stiffeners types: longitudinal (stringer), radial (ring), and helical with constant helical angles. The governing equations are derived baxsed on the classical shell theory, incorporating nonlinear stress-strain relations under thermal loading. The compatibility equations are solved using the Galerkin method and the method of undetermined coefficients to predict the thermal buckling loads and post buckling response. Numerical results validate the proposed model by comparison with previous studies and show that the reinforcement pattern significantly affects the thermal buckling performance. Among the configurations, the helical stiffeners yield the highest thermal resistance.