Cambodia covers an area of 181,035 sq km, among them, forests cover 53 percent, so there are abundant Insect diversities. Collecting expeditions of Insect were conducted from towns of Osam (first base camp, N 12° 04' 51.7" E 103° 12' 30.5" alt. : 549m) and Roveang (second base camp N 12° 19' 06.5" E 103° 3' 03.8" alt. : 53m) in Pursat Province, western part of Cambodia. As protected forest from government, these areas were almost natural conservation field. Pitfall trap, sweeping method, light trap and searching etc. were used to collect insect. Specially in this expedition, large or big sized beetles, more than 5cm body length, for example, Lucanidae, Cerambycidae, Elateridae etc., mostly collected from light trap in deep forest. Materials are expected more than 100 species belonging to 20 families but it was difficult to identification because of lack of references of this areas. Maybe lots of new or new recorded species will found from Cambodia. Among Coleoptera species, with big sized beetles as the central figure, photos for species of dominant, rare, nominated species of new or new recorded were introduced, and also collecting sites and activities were presented.