Abstract: In order to get a new method which can quickly and harmlessly measure the water content of wheat leaf, the effects of test voltage and frequency on physiological capacitances (Cp) and physiological resistances (Rp) of wheat seedling leaves with different water contents were investigated by a hand-made pair of parallel board electrical capacity type electrode. The results show that Cp is affected by water content but not by the test frequency under voltage 1.25 V and frequencies 15.7～150 kHz. There is a significant negative correlation between Rp and frequencies under 5～150 kHz. When the test frequency is fixed at 75 kHz and the voltage is changed from 0.1V to 2.5 V, Cp is not affected by the test voltages, but there is a powerful correlation between Rp and the test voltages. When the test conditions are fixed at frequency 75 kHz and voltage 1.0 V, both Cp and Rp are significantly related to the leaf water content, but Cp is a better indicator of leaf water content than Rp. Therefore, these physiological electrical characteristics can be used to quickly and harmlessly measure wheat seedling leaf water content.