鏡煤素反射率被廣泛應用於地層對比、變質度及有機物成熟度指標等，然常有被抑制的現象，影響油氣潛能評估。本研究以台灣三峽裕鋒煤(中新世石底層)透過膜煤素富集後，將煤樣製成薄片，在顯微鏡下以反射光與透射光交互觀察，以研究當膜煤素隱伏於鏡煤素之下對反射率的影響。 在透射光下發現當測量面的鏡煤素下方有膜煤素存在時，反射率呈現明顯下降，且反射率被抑制之情形與膜煤素和鏡煤素間的距離相關，即兩者間愈近，反射率測值愈低。 本研究亦以不同的加熱溫度、停溫時間以及加熱速率分別對44個煤樣(裕峰煤)進行熱模擬，並測得其加熱後的鏡煤素反射率。實驗結果發現，較高的加熱速率與加熱溫度確實造成鏡煤素反射率的上升，且以較快速率加熱，到達較高的溫度後，停溫時間(soaking time)對鏡煤素反射率才有較顯著的影響，且反射率隨著停溫時間的增加而有上升趨勢。 The reflectance of vitrinite is useful in many aspects, such as stratigraphic correlation, index of metamorphism and thermal maturation of organic matters. However, suppression of vitrinite reflectance had been reported and did affect the assessment of HC potential. Coal samples were collected from Yu-Feng mine in San-Hsia, North Taiwan. Exinite-enriched coal mixtures were prepared by density centrifuge of ZnCl2 solution and then made into thin sections and polished pellets. Samples were observed both in transmitted and reflected light under microscope. Reflectance of vitrinite particles were measured, so as to evaluate the effects of underneath exinite. The result shows that vitrinite reflectance was lowered due to exinite existed underneath the measuring surface of thin-layered vitrinite, especially when exinites were close to the vitrinite surface. 44 coal samples were heated in different rate, different temperature and different soaking time. The reflectance of vitrinite measured after heating indicate that the vitrinite reflectance increases with increasing heating temperature and heating rate. In addition, the reflectance was affected by soaking time when higher heating rate and temperature were performed. i.e, the longer the soaking time, the higher reflectance will be.