In order to give an insight into decomposition of ATP related compounds in stored fish, we re-examined ATP-related compounds and K-value change in bastard halibut (Paralichthys olivaceus) muscle when stored in different stored conditions focusing on the IMP decomposition by HPLC, and further studied factors that affect these changes, aiming at providing scientific guidance for preservation of fish. The result showed: Storage of flounder muscle block at 0℃ accumulated IMP as a major component indicating a quick conversion of ATP to IMP through ADP and AMP. IMP content decreased slowly in an early phase, while it dropped rapidly at the final stage of the storage (10 days) showing biphasic change. In ground fish meat, ATP degraded faster but there was no change in other ATP related compounds. Adding antibiotics (chloramphenicol) to samples at 0 d to prevent the growing of microorganism. It was obvious that IMP content decreased much slowly in the presence of the antibiotics showing linear change. When ground meat added with detergent (5% Triton X-100) to break cell membrane structure at 0 d, IMP decomposition was quicker than the control. Inclusion of Triton X-100 to ground meat also accelerated IMP decomposition at 10 and 20℃. The results indicated that the shape of stored fish affected ATP degradation but hardly had any effect on IMP decomposition. IMP decomposition in the later phase included the reaction by the exogenous enzyme coming from the microorganism growing at later phase. The existence of microorganism in later stored phase is the main factor that affected change of IMP decomposition. Modifying character of cell membrane by detergent also had effect on IMP decomposition.