The Mid-day Jerbil (Meriones meridianus) distributes in the northwest of China widely and is the dominant species in the desert rodent community. Its breeding characteristic is an important life history parameter which will produce great influence on population abundance. We conducted a 3 years filed study to investigate the population dynamic and breeding characteristics of Mid-day Jerbil in the south of Alxa using trap day method in four different areas with different grazing loads. We got the results as following: the meaning of the sex ratio was 1.09 ± 0.12, testicular decent rate was 0.74 ± 0.01, pregnancy rate was 0.21 ± 0.05, the number of foetus were 4.20 ± 0.32, breeding characteristics was 0.90 ± 0.22 in three years for the Mid-day Jerbil in the whole study area. The population density of Mid-day Jerbil was significant difference in four areas with different grazing load (grazing free < heavy grazing < rotational grazing < farmland) (Fig. 1); the highest sex ratio Appears in rotational grazing area, the next higher was recorded in farmland. The sex ratio collected in grazing free area was with minimum value (Fig. 2). The pregnancy rate in rotation grazing areas was significantly higher than those three other area, while the testicular descent ratio was significantly higher in heavy grazing load area than that in the other three areas and the lowest value occurred in the rotational grazing area (Fig. 3). No any difference was found between the mean embryo number of Mid-day Jerbil collected in the whole study areas with different grazing load (Fig. 4). The value of breeding index was the highest in rotational grazing areas of the four areas with different grazing loading (Fig. 5). The breeding characteristic, pregnancy rate and testicular descent ratio showed an obvious feedback for the population density but the feedback degree was difference in each area with different grazing load (Table 1). In conclusion, the Mid-day Jerbil′s showed a highest breeding potentials in rotational grazing area where was with the obvious density feedback and most suitability for the Mid-day Jerbil survival.