Abstract: In this paper, the microscopic and physiological characteristics of Murraya exotica and Spathiphyllum kochii leaves were studied in the indoor environment of high concentration formaldehyde. It was found that the relative electrical conductivity of the two tested plants increased from 16.2% to 44.4% and 9.2% to 21.1%, respectively, accompanied with the formaldehyde concentration of 0 mg·m^-3 increasing to 5.0 mg·m^-3. However, the concentration of chlorophyll for the two selected plants decreased from 2.9 mg·g^-1 to 1.8 mg·g^-1 and 2.8 mg·g^-1 to 1.9 mg·g^-1. The results from the scanning electron microscope(SEM) testing showed that the stomatal of the leaf became smaller and even closed or disappeared along with the increasing of formaldehyde concentration. The stomatic shapes between the two plants appeared much difference. The stomatal length of the two plants was range from 22.90 to 38.06 μm for Murraya exotica and from 20.23 to 18.80 μm for Spathiphyllum kochii. In addition, the change trends of stomatal density of the two plants were almost opposite. When the testing concentration of formaldehyde reached the highest value, the stomatal density of Murraya exotica reached highest value of 33 742·cm^-2, while Spathiphyllum kochii reached the lowest value of 549·cm^-2. The research of chlorophyll, conductivity and value of stomatal in this paper were important for the in-depth research of the response mechanism.