The 28 soil relative humidity measurements from March to July 2011 from DZN3 automatic soil moisture observation stations and manual observation are compared and analyzed. The results indicate that measurements from the automatic station are generally smaller than those from manual observation; the difference in the 30 cm soil layer is the smaller，those of the 20, 40, 50 cm layers the next, and those of 10, 60, 80, 100 cm soil layers the greater; the variation tendency is close in 10, 20, 80, 100 cm soil layers, and their correlation is good; the sensor sensitivity of automatic observation is relatively low for soil moisture changes, and the fluctuation range of soil relative humidity is small in the same soil layer. The results can provide an objective basis for evaluating the monitoring capability and revising and applying the monitoring data from the DZN3 automatic soil moisture observation station.