A puddling and soft cultivated layer of soil is always the favorable soil physical condition for the high yield rice in growmg stage,and after the middle stage of rice growth a more compact and hard soil condition is required for its better growth.The field study showed that the soil physical condition-puddling,softness,compact and hardness required by rice in different growing periods had its own characteristics.The hardness of paddy soil in relation to different soil texture,organic and rice roots was also studied.Results obtained denoted that the effect of soil texture on the a}oil hardness was more important than that of soil organic matter.A simulation test showed that when flooding after plough and harrow,the dynamic change of the soil hardness appeared firstly a high level,then decreased with the duration of submergence,and at last tended to a stable level.