Aims of the research were to: (i) assess of current status and effects of salinity intrusion on agricultural soil in Vinh Long province; (ii) identify factors that affect on the fertility of rice soils and mapping of s oil fertility degradation; (iii) suggest solutions to conserve land resources. In order to identify factors affecting on soil fertility and mapping of soil fertility decline, the research carried out some methos such as: participatory rural appraisal (PRA), describing soil profiles in the field, multiple criteria evaluation (MCE), analytic hierarchy process (AHP) and geographic information system (GIS). The results showed that: Saline intrusion has been occurring earlier and salty water has intruded deeper inside the mainland of Vinh Long province. Besides, the order of 11 factors affecting on soil fertility was determined. The map of soil fertility decline was also established with 04 levels: no decline, slight decline, moderate decline, severe decline. The research susggested some solutions to conserve land resources: the need for land management and investment policies to support farmers in agriculture areas where there has been severe decline soil fertility; support plant varieties and animal breeds suitable to each type of soil; increase using bio-fertilizers preparations to gradually replace chemical fertilizers minimize environmental impacts; to prioritize funding for land surveying and land evaluation.