Mass vaccination against viral infections such as mumps is a very noticeable and appropriate attempt in common health. Mumps infection has severe complications like deafness, infertility and meningitis. Attenuated live vaccine of mumps is produced and used to prevent the problems. Viral content in the monovalent vaccine is assayed with different methods. Nowadays international standards introduce microplate for titration of virus. In this study the different aspects were searched to assay vaccinal mumps strain, on microplate. Its results presented proper count of Vero cell and essential amount of viral inoculum to coculture, in certain concentration of CO2, on 96-well plate. Therefore with these ideal conditions, potency test of mumps virus was performed exactly, rapidly and economic with micromethod instead of cultivation in tube .Furthermore evaluation and reproducibility of the method accompanied with decreasing titer of < 0.5 log on microplate. The results showed the method is an efficient procedure for potency test in comparison with previous method.