Precipitation (P) and relative humidity (RH) are the most commonly used meteorological factors in the study of global dry and wet changes. It is of great significance for the researchers to grasp the change trends and their inconsistent patterns in different arid regions and different periods (annual, rainy and non rainy seasons), in order to accurately acknowledge the dry and wet changes in arid regions under the background of global warming. Based on the daily meteorological data of 20 meteorological stations in arid regions of north China from 1951 to 2018, the M-K trend test method was used to study the long term trends of P and RH at each station in the whole year, rainy season and non rainy season, and the inconsistency of the two trends was emphatically discussed. The results demonstrated that the stations with increasing P in different periods accounted for 70%-100% of the total number of stations, and the P of the annual, rainy and non rainy seasons increased by 0.02-4.42, 0.01-3.96 and 0.03-0.84 mm/a, respectively. Whereas the change trend of RH in different periods was almost opposite to that of P, and the proportion of stations with decreasing trend in the whole year, rainy season and non rainy season accounted for 85%, 85% and 90%, with a decrease of 0.01%/a-0.19%/a, 0.01%/a-0.17%/a and 0.01%/a-0.21%/a, respectively. The inconsistency of P and RH in the whole year and non rainy season periods reached 90%, whereas that in the rainy season period only accounted for 65%. It is found that the temperature T (annual and rainy season) and its increment ΔT (non rainy season) may be the key factors leading to the inconsistency between P and RH. In the context of future climate warming, the rising temperature will exacerbate the precipitation-evapotranspiration process during the rainy season and this problem will inflict an increasing number of arid areas.