The standard emission rate(ERs) of isoprene was quantitatively measured in situ from Quercus mongolica Fischer that dominates more than about 85% of domestic oak trees. The ERs values in spring and summer were similar to 64.4 and 58.1 (${mu}gC/gdw/hr$), respectively. The ERs in autumn, 7.06(${mu}gC/gdw/hr$), was about $8{sim}9$ times lower than those in spring and summer. The coefficient of determination ($r^2$) between ERs and $C_L;C_T$ ranged from 0.593 to 0.836. The correlation coefficients between the ERs and PAR. the ER and temperature suggested that ERs have strong correlation with PAR(photosynthetically active radiation) and temperature. In addition, the high values of PAR, temperature, and ERs were found in the time zone of $15:00{sim}17:00$(spring), $15:00{sim}16:00$(summer), and $14:00{sim}15:00$(autumn).