The synthesis of MIL-53 samples and encapsulation process of phosphomolybdic acid implemented using ultrasound at ambient temperature and atmospheric pressure. Analysis of the results showed that H3PMo salts have strong electrostatic interactions with the iron (III) lattice, which play an important role in reducing leaching from the compound. Characterization of newly synthesized nanocomposite was carried out using various techniques such as XRD, FT-IR, SEM, BET and ICP. The catalytic activity of the prepared nanocomposites, PMA@MIL-53(Fe), was tested through the esterification reaction of oleic acid with methanol under ultrasonic irradiation. Biodiesel production process using certain molar ratio of oleic acid/methanol, PMA@MIL-53(Fe) as catalyst (50-200 mg) containing different amounts of PMA (0-40%), at different reaction times (5-25 minutes) and ambient temperature under ultrasound conditions was optimized using CCD tab of Design Expert software. The results indicated that the synthesized composites show excellent catalytic activity.