Mineralization and fragmentation of leaf litter is important for understanding forest carbon cycle. We measured weight loss, mineralization and fragmentation rate of leaf litter of Fugas crenata from August 2011 to February 2012 in a cool temperate deciduous broad leaved forest. The study site was situated at Minakami experimental forest of Nihon University in Minakami, Gunma Prefecture. Dominant species were Fugus crenata and Quercus crispula in this study site. Beech leaf litter samples were taken from leaf samples on the study site in July 2011, We tagged the leaf litter to distinguish from other samples and measured leaf area and dry weight. The samples were put into polyethylene bag ,and set on the forest floor in August 2011．twenty samples were collected and measured respiration rate, leaf area and dry weight of each sample in each month. Although weight loss was observed, leaf area was not decreased in most of the samples in the first year of the experiment. Respiration rate of leaf litter in August showed the biggest value among the all months. Respiration rate was also decreased according to the (air or soil) temperature decrease.