Abstract: Abstract: Due to the complexity of soil and straw properties and the interactions among soil, straw and tillage tools, specific straw incorporating implements were designed and developed for particular working conditions. Different types of rotary tillers that adapted to different field states were produced in the last decades for straw burial. However, past efforts of assessment on rotary tillers were focused mainly on their soil working performances. Seldom has been done to assess the performance of rotary tillers and their effect on both soil disturbance and straw distribution in the tilled soil layer. A field experiment was thus conducted to compare the performances of rotary tillers on mediating soil and straw after rice harvesting. A mini-power rotor tiller was run on a platform developed for in-situ tillage test. Soil surface and micro-relief was measured with profilometer. Straw distribution was measured with a three-dimension coordinate tester. The measured results were transferred to Pro-E software, in which the measured data of straw distribution in soil were modeled and assessed. It was found that down-cut rotary tillage resulted into a gently humped soil surface over the tilled region, whereas the up-cut treatment led to a sink of soil surface in the mid region and the ridges along two sides of the tilled plot. Severe humping of fragmented soil was also observed in the up-cut tillage. It was therefore concluded that, for min-power rotor tillers in paddy field, the down-cut tillage provided better surface micro-relief than the up-cut. A higher percentage of buried straw, 88.91%, was acquired with the down-cut tilling. But it was low for the up-cut, which was 83.26%. The heaping-up of straw was also severe in the up-cut treatment, which was 33.02%, 8.19% higher than that from the down-cut. This indicated that the down-cut was more preferable for mini-power rotor tiller design compared with the up-cut. Analysis on the sectioned regions with the Pro-E revealed more straw concentration in the 5-10 cm soil layer for the down-cut tillage, while the up-cut treatment provided a more evenly distribution of straw in the soil volume. The modeled straw distribution in soil volume was sectioned into the grids at 3 different scales, and the total length of straw under the down-cut tillage revealed the smaller coefficient of variations (P<0.05). The up-cut tilling did prove its benefits, such as enhancing soil fragmentation and a highly leveled soil surface within the treated area. But the soil and straw heaping ahead of the machine was a main constraint for its adaptation to the paddy soil. Designing and developing of mini-rotor tillers for improving the performance of proper handling the soil and straw requires further investigation on the system optimization of soil structure, straw, tool geometry and working parameters.