Abstract: In order to research the relationship between spectral properties of delayed fluorescence and plant heat resistance, three different samples (Bean Jinghuang No.3, Queen’s Crape Myrtle Lagelstroemia indica L, maize s5-168) were used as materials to experimentally study on the plant delayed fluorescence emission spectra at elevated temperatures (25-55°C). The maximal values of DF emission spectra at 685nm and 730nm were marked as F685 and F730 respectively. After analyzing the characteristic of temperature response curve of F730/F685 ratio, the cause of the formation of inflexion on the temperature response curve of F730/F685 ratio, and the temperature responses of five chlorophyll fluorescence parameters, it was concluded that DF emission spectra varied with the temperature-stress, and the responses of F730/F685 ratio of DF emission spectra to the temperature for the different samples could be a new and useful judgment to identify and evaluate the heat-resisting property of the samples. Moreover, the temperature inflexion of the temperature response curve of F730/F685 ratio could be a new identification index of plant heat resistance.