Abstract: Some factors and methods that can improve the photographic properties of the direct positive photographic emulsion were studied.It was found that the structure characteristicsof the silver halide crystal has significant effect on the properties and the emulsion with multi-lay-er crystals may be the best one for direct positive imaging.The prefoging process is important,because it can influence the form and the distribution of the fog center.Changing the way andmeans of prefogging may effectively control the maximum density and the sensitivity. The rever-sal speed increases greatly when an organic desensitizing dye is used.The effect of iedide distribution in the silver halide crystal is notable. When iodide is located at the grain surface,the sen-sitivity of the direct positive emulsion increases obviously.