Abstract: The expanded vermiculite (EV)-gypsum thermal insulation composites were manufactured by compression moulding. The effects of flake diameter and preparation methods of expanded EV, mass ratio of EV to gypsum (R_m) on the thermal and mechanical properties of EV-gypsum composites were investigated. The results indicate that the thermal conductivity (λ) and compressive strength of the samples decrease with the increase of EV flake size, and increase as a quadratic function of rising R_m. The samples containing EV expanded by microwave chemical method present a better thermal insulation property (λ=0.082 W(m·K)^-1) than that of the ones filled with microwave exfoliated EV (λ=0.097 W(m·K)^-1). The EV-gypsum composites can play an important role in the fields of heat insulation, acoustic isolation and moisture adjustment.