Using the collected 433 heat flow values,we estimated the bases of methane hydrate stability zone (BHSZ),in northern South China Sea (NSCS).Through comparing BHSZs with the depths of bottom simulating reflectors (BSRs),in Shenhu Area (SA),we found that there are big differences between them.In the north of SA,where the water depth is shallow,many slumps developed and the sedimentation rate is high,it appears great negative difference (as large as-192%).However,to the southeast of SA,where the water depth is deeper,sedimentation rate is relatively low and uplift basement topography exists,it changes to positive difference (as large as +45%).The differences change so great,which havent been observed in other places of the world.After considering the errors from the process of heat flow measurement,the BSR depth,the relationship of thermal conductivity with the sediments depth,and the fluid flow activities,we conclude that the difference should be not caused by these errors.Such big disagreement may be due to the misunderstanding of BSR.The deviant "BSRs" could represent the paleo-BSRs or just gas-bearing sediment layers,such as unconformities or the specific strata where have different permeability,which are not hydraterelated BSRs.