Abstract: Temperature plays a vital role in the growth of plantlets in vitro. To enhance the photosynthetic photo flux density can cause a drastic change in temperature. To probe the effects of light intensity on temperature in the microenvironment, changes in temperature of several selected points were measured during different photosynthetic photo flux densities (PPFD). Changes in temperature and patterns of heat balance were analyzed. The pattern of heat balance for microenvironment in vitro was constructed. The results of the experiment showed that the increase in temperature resulting from the improvement in PPFD was higher than our expectations. Therefore, it is necessary to decrease the temperature in the micro-environment. The analysis shows that the temperature control for the bench and the gas inside the culture box offers an effective way to decrease temperature in the microenvironment.