Abstract. Utilizing crushed limestone dust; the by-product of crushing limestone plant for producing non-fired wall tiles is the objective of this research. The main raw materials of non-fired wall tiles consist of laterite soil, fluvial sand and Portland cement. The crushed limestone dust has been used as the substitute material of non-fired wall tiles for enhancing their bending strength. In this experiment, four groups of formulas have been constructed. Firstly, crushed limestone dust has been mixed into the basic formula for substitution of laterite soil. Secondly, crushed limestone dust has been used for substitution to river soil of the basic formula. Thirdly, it has been substituted to Portland cement in the basic formula. Finally, the best formulas of the first three groups has been selected and mixed up to make the new formulas. After mixing the raw materials of selected formula, forming specimens by uni-axial pressing at 100 bar has been performed. Then, they have been aged for 1 week at the room temperature. After that, testing the specimens' properties has been carried out. They are bending strength and water absorption which comparing with Thailand Industrial Standard (TIS) 614-2529. The experimental results show that adding the crushed limestone dust to the basic composition has an effect on the bending strength and water absorption. The compositions of the best formula are laterite soil 55%, fluvial sand 7.5%, Portland cement 22.5%, and crushed limestone dust 15%. It gives the bending strength by 2.32 MPa, water absorption 3.20%. The water absorption property can pass the TIS standard, but bending strength could not pass. The estimated cost of raw materials is 0.09065 THB/100 g.