The acid activated montmorillonite clay and titanium dioxide (P25) are prepared as heterogeneous catalysts by comparing to concentrated H2SO4 for the esterification between stearic acid and methanol. The five different concentrations of sulfuric acid (0.5, 1.5, 2.5, 3.5 and 5.0 M) are studied for the activation of montmorillonite clay. As a result, 3.5 M of sulfuric acid doped on montmorillonite (2.5 M H2SO4/mont) showed 45% yield which is the highest yield by comparing to other concentrations of acid on the clay. The 2.5 M of sulfuric acid doped on P25 (2.5M H2SO4/P25) is also investigated and it showed the higher catalytic activity (49%yield) by comparing to 2.5MH2SO4/mont (38%yield). It indicated that TiO2 is more powerful catalyst than montmorillonite. This may be due to the more surface area of titanium dioxide. Moreover, the reusability of 2.5 M H2SO4/P25 is also investigated and it can be use about 3 times with slightly decreasing of %yield.