Abstract: Photographic effect of Sn(Ⅱ) ions doping in a silver iodobromide emulsion containing 4.0 mol% of Ⅰ^- was studied.Experimental data showed that photographic speeds increased and fogs decreased for either shorter or longer exposure times when a trace of Sn(Ⅱ) ions, of which contents were from 3.84×10^-3mol% to 3.84×10^-2 mol%, were added in the emulsions during precipitation and physical ripening stage.Low intensity reciprocity failure (LIRF) of the emulsiom, on the other hand, diminished due to the same reason.The influence of the concertration of Sn(Ⅱ) on LIRF was also, studied.