Lakes are one of the major carbon pools in biosphere. Understanding lake metabolism processes would improve the prediction of effects of environmental changes and external disturbances on ecosystem functions. Gross primary production (GPP), ecosystem respiration (R), and net ecosystem production (NEP) are used as the key parameters to elucidate the dynamics of lake metabolism and the carbon balance within various lake ecosystems. We aimed to explore the seasonal dynamics of a subtrophic, subapline lake metabolism and to investigate how the typhoon season (from June or July to October) affecting the lake metabolism. This study was conducted in Yuan-Yang Lake (YYL), a well preserved high mountain forested lake in Taiwan. A buoy equipped with dissolved oxygen (DO) sensor was deployed in the deepest site of YYL to collect high-frequency (every 10 minutes) limnological and meteorological data, including DO, wind speed, air temperature and light intensity, for lake metabolism estimation. We used the Odum model to estimate the time series of GPP, R and NEP from April 2004 to October 2005. Results indicated that YYL is a net heterotrophic ecosystem (annual mean net ecosystem production is-39.6 μmole O2 m^(-3)). Both GPP and R showed obvious seasonal variations and were the highest in spring and autumn, but lower in typhoon season (from June or July to October) and winter. Compared to the summer peaks, seasonal averages of GPP and R decreased by approximately 50% and 25%, respectively, during the typhoon season.