Abstract: The paper describes the variation of some characteristics of the nuclear emulsion such assensitivity, fog density and latent image stability influenced by adding ascorbic acid into the fi-nished emulsion N-4. A comparative study of latent image stability is made between Fuji ET-7Bnuclear emulsion and our's under different temperature and relative humidity. The result indi-cates that the addition of ascorbic acid obviously improves the latent image stability of the emul-sion N-4. The Fuji ET-7B emulsion and the emulsion N-4 containing ascorbic acid have similar la-tent image fading quality at lower temperature while the Japanese sample does better at roomtemperature.