This thesis performs the information of existing management practices practiced by the smallholders who cultivate their oil palm plantation around Raja Musa Forest Reserve through surveying. The face to face interview of survey was conducted randomly on the smallholders found in the study area The collected data was being interpreted through the three main objectives of this study: determination of the Best Management Practices (BMP's). the address of opportunities and constraints of smallholders in cultivating their oil palms and the perceptions of the smallholders on the correlation between environmental degradation occurred in Raja Musa Forest with their existing management practices. This study reveals the weak of existing management practices practiced by the smallholders where the plantations suffered from the impacts of environmental degradation. The fires prone and flooding were frequently happened in the study area according to the climate factor and improper water management. The low fertility of peat soil caused the higher consumption of fertilizer and the low bulk density of peat soil caused the peat subsidence at once led the formation of leaning and fallen oil palms. The excessive basal stem roots exposed to the atmosphere may cause the low upiake of nutrient from the soil. Thus, these reasons may lead to the low yield productions of Fresh Fruit Bunches produced by each palm. It was found also the smallholders did not aware so much of BMP's and they still practice the old agronomic practices which contribute to the environmental degradation. It was applicable if BMP's as one comprehensive guideline for oilpalm cultivation on peat which can show the positive response to increase the yield production while reduce the environmental impacts in the study area. Thus, the information provided through this study are useful to address the main issues and challenges currently faced by the smallholders before the BMP's wilt be mitigated or conducted in oil palm plantation around Raja Musa Forest Reserve.