Abstarct: Transmissivity and specific yield are important hydrodynamic parameters in unconfined aquifer. These two parameters can be assessed with different methods which the most important and reliable method in determination of hydrodynamic paremeters is usage of pumping test results. However, because of some limitations that exist in use of pumping test results, use of alternative methods, such as logging, specific capacity of well, testing unique wells, geoelectric method and etc., is impotant. According to the absence of sufficient numbers of pumping test data-set in Mashhad Plain, the values of transmissivity and specific yield of unconfined aquifer in this plain have been assessed using existance drilling logs. According to the obtained the values results of transmissivity in Mashhad Plain aquifer vary from 50 m2/d to 255 m2/d. Also the values of specific yield in this aquifer is fall between 0.02 and 0.07. The values of transmissivity and specific yield of Mashhad Plain aquifer yielded by drilling logs have two advantages in comparison with those valuse obtained using pumping test data. Firstly, the number of drilling logs are 26 that is more important ralative to 3 available pumping test cases in this plain. Secondly, values of transmissivity and specific yield obtained using the drilling logs in any portion of the plain are more or less the same where as those obtained using pumping test analysis include considerable discrepancies in the same location of the plain. The reason for such discrepancies could be rated to the inaccuracy pumping test of data or errancy inusing of these data.