Research on the determination of water content of tea by using low field NMR instrument has been conducted. The purpose is to develop a more rapid, accurate and nondestructive method to measure the water content of tea. In this experiment, six pure water samples with different weights were prepared as standard samples to test their FID signals. FID signal data were fitted to a line equation. Five tea samples were prepared to test their FID signals and calculate the water content of tea by the fitting equation, then compare the results with national standard method. Result showed that the determination of water content of tea by low field NMR could obtain a more rapid and accurate result. The result by low field NMR is about 1% higher than that of the national standard method, because the drying method can’t dry the bound water completely,but the NMR measures both the content of free water and bound water.