Heath forest or Kerangas is one of the forest types in Borneo and occurs on very poor, acid soils, usually podsolic and consisting of coarse, white sand overlying, at varying depths, a thick, hard, extremely acid pan. The tree species composition in the heath forests in Sarawak continuously studied but comparison among the sites is seldom be conducted. Therefore, the objective of this study is to compare the tree species comparison of two heath forests in the southern part of Sarawak. A 1-hectare plot with 100 quadrats of 10 m x 10 m size established in each of the heath forests in the southern part of Sarawak, Kelingkang Forest Reserve (KFR) and Samunsam Wildlife Sanctuary (SWS). A total of 1,251 trees with a diameter of 10 cm and above were recorded with Dipterocarpaceae as the main family identified as the highest individual in both sites. KFR and SWS shared a few same species that are synonyms in kerangas such as Hopea kerangasensis and Whiteodendron moultonianum.  Endemic species such as Dryobalanops fusca and Vatica adenanii are among the species recorded during this plot assessment. Conservation of the kerangas forest is important to ensure the sustainability of the species for future generations.