[Objective] The black soil region of Northeast China is an important commodity grain production base in China. The long-term high-intensity utilization and unplanned agricultural cultivation measures led to serious soil fertility decline, grain yield reduction, and soil erosion in some areas. Soil erosion and land degradation in the black soil region seriously restricted the development of the agricultural economy in Northeast China. This threatened national food production and security. Ridge tillage is the most common cultivation method in the black soil region of Northeast China. However, the long-term effects of different ridge direction on slope erosion and deposition has never been evaluated. Therefore, understanding soil erosion and deposition on slopes with different ridge directions is of great significance for the development and deployment of soil and water conservation measures and the control of soil loss in the black soil area of Northeast China.[Method] ¹³⁷Cs is an artificial radionuclide produced by atmospheric nuclear test and nuclear leakage. Its half-life is 30.2 years. The nuclide is strongly adsorbed by clay particles in soils after settling to the surface, and it is difficult to be leached by water. This implies that it only moves mechanically with soil particles. Therefore, it is regarded as a good tracer and widely used in the study of soil erosion rate. In this study, ¹³⁷Cs tracer technology combined with wavelet analysis method was used to study the spatial variation of soil erosion and deposition rate on slopes with different ridge planting directions.[Result] (1) The average concentration of ¹³⁷Cs on slopes with horizontal and longitudinal ridges was 1 802 Bq·m^-2 and 1 770 Bq·m^-2, respectively, which were lower than the local background value of 2 417 Bq·m^-2. (2) The slope erosion and deposition rate were between -700 to 2 662 t·km^-2·a^-1 with an average of 1 341 t·km^-2·a^-1 on slopes with horizontal ridges, and that on slopes with longitudinal ridges was between -726 to 3 327 t·km^-2·a^-1 with an average of 1 466 t·km^-2·a^-1. These results showed that the average erosion rate of slopes with horizontal ridges was lower than that with longitudinal ridges. (3) Different periodic change of erosion and deposition on 140 m long slopes were observed. There was a 45 m main period and a 75 m secondary period of erosion and deposition on slopes with longitudinal ridges, while only a 45 m main period was observed on slopes with horizontal ridges.[Conclusion] The periodic change of erosion and deposition on slope surface is mainly caused by the change of transportation capacity of rainfall-runoff and snowmelt runoff along the slope. Different degrees of soil erosion occurred on slopes with different ridge directions, and the slopes with horizontal ridges showed less soil loss than those with longitudinal ridges. Although soil erosion in the study area was mild, its average soil erosion rate is far greater than the allowable soil loss (200 t·km^-2·a^-1)in the black soil region of China. Thus, there is an urgent need for comprehensive control of soil erosion in this area. This study could provide a scientific and theoretical basis for the precise layout of soil and water conservation measures such as; (i) reinforcement of ridge platform and (ii) arrangement of contour plant belt on strong erosion positions of slopes. This could prevent the destruction of ridges by runoff and effectively reduce slope soil erosion.