To prepare a silver halide emulsion having high sensitivity and excellent in rapid processing, to obtain silver halide photographic sensitive material containing the silver halide emulsion, photosensitive material for heat development and photosensitive material for activator development and to provide an image forming method using those materials.

In the silver halide emulsion containing a dispersive medium and silver halide grains, a silver chloride content of the silver halide grains based on the total amount of silver is ≥50 mol %, flat platy grains having (100) faces as principal planes and an aspect ratio of ≥2 account for ≥50% of the total projection area. The silver halide emulsion is formed through at least (a) a step for forming core grains, (b) a step for forming anisotropic growth defects by adding halogen different from the core grains in composition and (c) a step for growing flat platy grains. The methionine content of a dispersive medium in the step (c) is ≤70% of that in at least one of the steps (a) and (b).