[Background] Universal Soil Loss Equation (USLE) is an empirical model widely used in the domain of soil erosion by water. And the rainfall erosivity (R factor) is a basic factor in USLE and the revised universal soil loss equation ( RUSLE). The soil erosion and rainfall factors are closely related. The accuracy of the calculated results of rainfall erosivity will directly affect the quantitative study of soil erosion. The calculated results by the classical models are accurate, however, the calculation process is cumbersome, and the data used in the calculation is large and difficult to be obtained. Calculation of rainfall erosivity using simplified models is convenient, but the result is not accurate enough. [Methods] The differences of rainfall erosivity calculated by 8 different models were analyzed, then the simplified models generating the closest values with classical models were modified, and then the simplified models after modification were used to analyze the temporal and spatial distribution characteristics of rainfall erosivity. The main methods used in this process were mathematical statistics and model difference analysis. [Results] 1) Compared to the simplified models, classical models were more accurate to estimate the rainfall erosivity in the loess hilly and gully region, the main reasons resulting in this were as, the impact degree of rainfall intensity factor was much higher than the rainfall factor on soil erosion in the loess hilly and gully region, while rainfall intensity was not considered as an impact factor in the simplified models, and the calculation in the simplified models was carried out by daily rainfall and monthly rainfall data. 2) The fitting model y = 0.849x - 29.651 improved the simulation precision of the simplified model of rainfall erosivity by Zhang Wenbo (Goodness of fit was 0.734). The rainfall erosivity of the loess hilly and gully region of Northern Shaanxi Province during 2006 2012 showed a rising trend. The rainfall erosivity of the upstream of Fenchuan River Basin and Qingjian River Basin was relatively high and the rainfall erosivity of the downstream was in second; the rainfall erosivity of the downstream of Yanhe Basin and Dali River Basin was relatively high, and the rainfall erosivity of the upstream was in second. [Conclusions] The simplified rainfall erosivity models after modification may be used to better estimate the rainfall erosivity in the loess hilly and gully region,and by which the manpower, time and cost would be saved; moreover, the favorable simulation accuracy can be obtained, thus they can be used in large scale and provide a scientific basis for the soil and water conservation work in the loess hilly and gully region and even the country-scale investigation of soil erosion. The rainfall erosivity in the loess hilly gully region is calculated better by simplified model after modification, as result, the temporal and spatial distribution of rainfall erosivity in the loess hilly and gully region are high and uneven as a whole from 2006 to 2012.