Abstract: The relationships among the initial water content, compactness, cover load and expansion rate are studied through expansion experiments in the state of <>K₀ stress for Handan strong expansive soil. The expansion rate under small pressure is declined sharply relative to unloading. The expansion rates under small loading (<6.25 kPa) and large loading are difficult to be described by one equation. The formulae of no-load expansion rate and loaded expansion rate are established respectively based on the compactness and the initial water content. The expansion rate between 0~6.25 kPa can be calculated by linear interpolation according to the no-load expansion rate and that under the pressure of 6.25 kPa. Finally, an expansion model in the state of <>K₀ stress is established. This model is available to soil for different expensive classes and of promotional value.