【Objective】The ecological environment of Loess Plateau is fragile, and the change of cultivated land soil quality directly affects the level of soil productivity. Tianzhen County, a typical county in the north of the Loess Plateau, was selected to study the spatio-temporal evolution of soil organic matter and total nitrogen and its influencing factors, which provided a theoretical basis for improving the quality of cultivated land and protecting agro-ecological environment.【Methods】Based on cultivated land quality data in 1983, 2008 and 2019, geostatistics were used to analyze the spatio-temporal evolution of organic matter and total nitrogen in Tianzhen County.【Results】In the past 36 years (1983-2019), soil organic matter and total nitrogen contents in Tianzhen County showed the characteristics of overall increase and rapid increase in the later period. The average annual increase of organic matter and total nitrogen content in the early period (1983-2008) was lower (0.20 g·kg-1 and 0.01 g·kg-1), and the average annual increase in the late period (2008-2019) was higher (0.29 g·kg-1 and 0.03 g·kg-1), respectively. The spatial distribution characteristics of organic matter and total nitrogen are similar, showing a low pattern in the west and a high pattern in the east, and a rapid change rate in the northwest and central parts.【Conclusions】Fertilization and straw returning were the main factors leading to the change of organic matter and total nitrogen content in Tianzhen County. Therefore, increasing organic fertilizer application combined with local conditions, popularizing straw returning and rational application of nitrogen fertilizer could rapidly improve soil fertility in cultivated land.