Abstract: Pre-consolidation pressure was usually measured by fast uni-axial compression test on confined cylindrical soil, the determination of which provided a basis reference for soil structure protection and a theoretical foundation for the correct selection of axial load, as well as the design and field application of agricultural machineries. A field experiment was conducted in Nanjing Jiangpu farm to measure the pre-consolidation pressure. Its value was 58.84- 69.19 kPa for undisturbed soil and 69.15-100.1 kPa for compacted soil with a tractor. The results showed that wheel rolling increased soil pre-consolidation pressure and thus destroyed soil structure. The currently used agricultural machineries usually have a contacting pressure of 70 kPa above, while the measured value was around 60 kPa. It is concluded that the application of these machineries will caused soil compaction and soil structure destruction.