Abstract: The purpose of this research is to determine the effect of soybean seed of different sizes and sample quantities on the parameters of a resonant cavity and microwave frequency, and to evaluate the feasibility of the system for measuring moisture in individual kernels.When electromagnetic wave and dielectrical body work mutualy, its energy consumption is connected with the size,shape and relative dielectrical constant of the body. While the moisture content of the body varies the wave frequency is shifted with it. Because relative dielectrical constant of water is different from that of most of the moisture-absorbed dielectrical materials, the effects of water and of dry dielectrical materials can be separated and ultimately, the relative moisture of dielectrical material, such as,soybean or grains can be measured.It was proved by the priliminary research that the microwave resonant cavity technique is a valuable tool to measure the soybean moisture of kernels. As measurement is done by measuring the shift properties of resonant frequency and coefficient of transfer, therefore,it does not require very high stability of the measuring system. The technique may also be used for the measurement of moisture of corn, wheat and other seed kernels.