In this study, from the fact that forest area in PhuQuoc district tends to decrease in terms of quality andquantity for various reasons, the demand for information onthe variation of forest area in the past as the basis for effectiveforest management. This study applied Landsat imagery (5, 7,8) to generate the forest cover maps at 3 different dates in1993, 2003 and 2013 using object-based approach, thenchange detection analysis is used for mapping forest coverchanges from 1993 to 2013. The results showed that Landsatdata reflects quite accurately the current state of forests inPhu Quoc district (with overall accuracy of 75.38%). Forestarea in 1993 is 50,049 ha but in 2003 remaining forest area is38,765ha (decreased 11,284ha), and continue to decrease to37,476ha in 2013 (decreased 1,289ha), total forest area hasdecreased from 1993 to 2013 is 12,573ha. The largestdeclined forest area occurred at Cua Duong commune (3,035ha), and least at Ganh Dau commune and An Thoi town (671ha). The study provided the baseline data to help localauthorities in planning the remaining forests on the island aswell as the forest development strategy in the future.