We have surveyed monthly diversity and seasonal prevalence of Macrolepidoptera in Wol-ak-san [Mt.] for the period of four months from May to August in 2010. Although it is not a part of KLTER/ME and KLPS study in Wol-ak-san conducted in recent few years, this year's data may be comparable with the previous ones as the collection sites and dates are very similar. The three representative vegetations are Quercus mongolica-, Quercus variabilis- and Pinus densiflora-formations, abbreviated as QM, QV and PD, respectively, and we collected exclusively larger moths with bucket-type of light traps for quantified survey. In 2010, as a result, QV showed higher species diversity and specimen number than QM or PD although the differences between QV and QM are very subtle. The result is very similar to the result in 2009. The only difference in 2010 over 2009 is that the number of species, not specimens, has been increased 1.5 times, and this may be caused by the inclusion of July records, which has been usually deleted due to heavy rainy season causing poor collection records. The number of species in Noctuidae was the highest in 2010, about twice more than that in 2009, but the dominant species in 2010 were either Pyralidae (Nacoleia commixta or Bradina geminalis) or Geometridae (Arichanna melanaria). We are still experiencing decline of specimen numbers: 567 specimens collected in 2010 while 651 in 2009 and 874 in 2008, which was already a huge reduction compared to over 2500 specimens in 2007.