Objective  The paper aims to clarify the spatio-temporal characteristics of soil relative humidity in 0 - 50 cm soil layer in Shandong Province and its relationship with meteorological factors, so as to provide support for agricultural production development.

  Method  Daily soil relative humidity data and meteorological observation data from 2013 to 2019 observed by 139 automatic soil moisture observation stations in Shandong Province were used to explore the spatial changes of soil relative humidity at different depths at different time periods by using inverse distance weight spatial interpolation, and the correlation analysis was carried out between the relative humidity and meteorological elements.

  Result  The relative soil moisture distribution of cultivated land in Shandong Province gradually decreased from west to east, and the vertical distribution showed an increasing trend with the deepening of soil layer. The relative soil moisture of 0 - 30 cm layer in one year gradually increased from January to August, and gradually decreased from August to January of the next year. The soil relative humidity of 30 - 50 cm layer had little change. The average annual relative soil moisture of each soil layer showed a decreasing trend year by year. There was a significant positive correlation between the monthly average relative humidity of each soil layer and the monthly precipitation in summer and autumn.

  Conclusion  The monthly average relative soil moisture of cultivated land in Shandong Province changed significantly in horizontal and vertical directions, and the vertical changes mainly occurred in the 0 - 30 cm soil layer. The annual average relative soil moisture showed a trend of decrease year by year from 2013 to 2019, and the relative soil moisture was mainly affected by precipitation.