It is concerned significantly with the agricultural practice whether the alkalization of salt-affected soils in coastal region occures after their reclamation.The present investigations both in fields and laboratory deal with this respect of the salt-affected soils in coastal region in Jiangsu,Zhejiang and Liaoning provinces.The results are summarized as follows:1.In the process of intensive salinization resulted from the action of underground water with high mineralization rate because of the process of Ca⁺⁺ on soil absorptive complex exchanged by Na⁺,the alkalization will takes place in coastal salt-affected soil.It's alkalinity is positively correlated with salt content of the soil.Generally,the coastal salt-affected soil does not show the characteristics of alkaline soil due to the influence of a large quantity of neutral sodimn salt in soil solution.2.Under the process of soil evolution or the conditions of its reclamation and utilization,dealkalization of the soil will be taken place with the proceeding of desalinization in the soil,which means the decrease of absolute content of exchangeble Na⁺ on soil absorptive complex and the decline of alkalinity of the soil.So long as appropriate and reasonable measures of water management,agricultural and forest practice are adopted in accordance with the local conditions,the soil alkalization could be controlled.3.The phenomenon of increase of soil pH and total alkalinity in the process of desalinization of coastal salt-affected soils should be analyzed by the view point of soil genesis.This phenomenon may occur under the processe of soil desalinization and the alkalization taken place simultaneously,and it may also occur under the process of dealkalization and desalinization.In the later case,with the leaching of large amount of neutral salts,the temporary increase of pH and total alkalinity may be induced by the hydrolysis of exchangeable Na⁺ on soil absorptive complex,which just illustrated the beginning of soil dealkalization and not the occurence of alkalization.It is also proved by the data of our investigations that the alkalinity decreased with the further developing of desalinization of the soil.The dealkalization process occured simultaneously with the desalinization in coastal salt-affected soils may be related to the CaCO₃ and biological activities in the soil.