An indoor rainfall simulation experiment was designed according to the landform of the slope lands around the Miyun Reservoir and carried out with the aid of the ICP-MS mass spectrum analyzing technology, to determine regularities of the loss of seven different kinds of metal cations with surface runoff from fields of cinnamon soil different in slope under different rainfall intensities and durations. Results showed that when the slopes and rainfall durations were the same, cation losses increased gradually with rainfall intensity, which fitted more K, Mg, Fe and Mn. When intensities and durations of the rainfalls were the same, the occurrence of maximum cation losses disagreed with the slopes, but when the rainfall intensity was 120mm/h and slope was 25° the losses of K, Na, Ca, Mg, and Fe all reached maximum. When the slopes and the rainfall intensities were the same, the losses of cations increased with the duration of rainfalls. Relativities were also found between the total losses of different cations with the change in slope. For example, when the rainfall intensity was at 60mm/h and 120mm/h, the correlation coefficients of K losses and Ca losses were 0.974 and 0.953 separately. The loss of each cation within a duration was little related to volume of the runoff. But when the rainfall intensities were the same, quadratic curve relations existed between hourly total losses of seven different kinds of cations and volumes of runoff with the slope, and the square of multiple correlation coefficient is bigger than 0.9.