In recent years, the use of RFID technology has gained popularity in the timber industry for wood-log monitoring. Harvested wood-logs are stored for different time periods before being processed. As a result, the moisture content in the stored wood-logs varies compared to the freshly-cut wood and it must also be noted that the moisture content of freshly cut wood differs from one log to another. Apart from storage time period of wood-logs, the environmental factors such as temperature, rain, snow and sun also contributes to the variation in the moisture content of the wood-logs. This variation of the moisture content changes the dielectric constant of the wood and hence, influences the characteristics of the RFID antenna. In this paper the impact of variations in moisture content in wood and its effect on the performance of the RFID antenna are studied.