The invention relates to an observing method and an observing device for the injection volume in an APG process and an APG die. The observing method comprises the following steps: performing section division on the volume of a die cavity in the vertical direction, observing the flash change of a die closing joint in injection, wherein the flash position reflects the position of an injection material in the die cavity, recording the passing time of a flash under sectioned volumes, namely the actual injection time under the sectioned volumes, and under the condition that the given injection speeds are consistent, determining the estimated injection time under the sectioned volumes, and adjusting the injection pressure to enable the actual injection time under the sectioned volumes to be consistent with the corresponding estimated injection time under the sectioned volumes. The volume of the die cavity is divided, the injection time under the preset sectioned volumes is determined, the injection speeds under the sectioned volumes are indirectly quantized, the injection time under the sectioned volumes is adjusted through the injection pressure, and the condition that the injection speeds under sectioned volumes are consistent is ensured.