EPS thermal insulaton mortar(ETIM) has become a new building material, it not only has an eximious capability of thermal insulation but also has a good working ability. The performance of ETIM is improved, besides, attention to cost control is paid. With the help of orthogonal design and statistics, water absorption, compressive strength and thermal conductivity are discussed and project of mix proportion is obtained. Compared with the old mix proportion, not only the cost of the new one is reduced by 1.7%, but also the performance has been enhanced.