Abstract: Abstract: Evaluation of plant leaf senescence is one of the core issues of life science research, which is generally based on the physiological indicators such as chlorophyll content，malondialdehyde (MDA) content. This evaluation method requires to destroy plant cells，resulting in inaccurate measurements and many other issues. Non-destructive testing and evaluation of leaf senescence has not been resolved. Plant cells in life activity will produce ultraweak photon emissions which include spontaneous photon emission and delayed photon emission induced by external light. The ultraweak photon emission of living cells is closely related with many processes such as physiological metabolism, photosynthesis, and cell division. Through analysis and interpretation to the ultraweak photon emission of plant cells, a new method for non-destructive testing of plant leaf senescence could be proposed. For this purpose, spinach leaves in vitro were treated with H2O2. Spinach leaf senescence caused by H2O2 stress and the ultraweak photon emission of spinach leaf under H2O2 stress were studied in this paper. The results showed that the spontaneous photon emission of spinach leaves increased with the extension of H2O2 stress time and was positively correlated with changes of MDA content in leaf, with a correlation coefficient of 0.90415, and the changes of spontaneous photon emission in leaves reflected the changes of membrane lipid peroxidation degree in plant leaves. The study also found that the change of delayed photon emission induced by external light also occurred in the process of H2O2 stress. Compared with the control group, the delayed photon emission of spinach leaves decreased rapidly. According to the biological significance of spontaneous photon emission and the delayed photon emission of plant cells induced by external light, using the ratio of integrated intensity of the delayed photon emission to the spontaneous photon emission as a state parameter to describe the overall state of cells, it was found that the changes of cell state parameter based on ultraweak photon emission of cells were positively related to the changes of chlorophyll content in cells in the process of leaf senescence under H2O2 stress, with a correlation coefficient of 0.91437. This result suggested that the degree of cells senescence in leaf could be speculated through the change of cell state parameter based on ultraweak photon emission of cell, so as to realize non-destructive testing and evaluation about the degree of cells senescence of plant leaves. The photonics method of leaf senescence evaluation proposed in this paper needs to be verified in more experiments in different plant leaves.