The esterification of free fatty acids (FFA) found in vegetable oils with alcohol using an acid catalyst is a promising method to convert FFA into valuable ester and obtain a FFA-free oil that can be further transesterified using alkali bases. In this work, the direct esterification reaction of FFA in crude palm oil to ethyl ester by continuous microwave was studied and the effects of the main variables involved in the process, amount of catalyst, reaction time and the molar ratio FFA/ alcohol were analyzed. The optimum condition for the continuous esterification process was carried out with a molar ratio of FFA to ethanol 1:24, using 1.25 wt% of H2SO4 as a catalyst, microwave power of 77 watts and a reaction time 90 min. The esterification process that has been studied shows that the amount of FFA was reduced from 7.5 % wt to values around 1.4% wt, similar results were found out for conventional heating but 240 minutes of reaction time. The results show that microwave heating has effectively reduced the reaction time. The esterified crude palm oil is suitable to perform the transesterification process.