In this work, the grain dielectric constant estimation method is investigated against the effect of air between the grains. The dielectric estimation method is based on sensitive capacitance measurements on humid grains. The method assumes that there is no air gap between grains. However, it is not possible to get rid of air gaps in a grain sample under measurement. Therefore, neglecting air effect in the measurement may lead to some measurement errors. In order to decide the validity of the result, the effect of air gaps between grains should be analysed and reduced to an acceptable level. The method is based on the mathematical model of the estimation algorithm. The air effect is added to the model and analysed for reducing errors. The result is promising and the error due to air can be reduced under certain conditions.