The quality of wood is determined by water contained on it, and known as wood moisture. To determine the wood moisture, it requires to measure the moisture. Methods used to know the moisture are moisture meter for indirect measurement and Oven Method for direct measurement. In this research, Resistance Method is used to measure the water-electricity of the wood. In this case, value of the voltages is measured. The wood moisture measurement system tools use aligned cooper plat as the censor. The physics principle of this aligned cooper plat is based on resistence changes as the result of the capability water flowing. This censor was tried out at type of wood called Mahoni and it showed that the voltage output had inversed linear upon wood water moisture with relative error 2,1 %. There was a strong relationship between wood water moisture and electricity voltage. By using a simple linear regression. We had found the mathematical model as = 4,263 – 0,108X for Mahoni with correlation index ( r )= 0,992. Where Y was electricity voltage and X was water moisture.