Abstract: Early worldwide experiments showing the validity of effective stress principle in saturated clay are concisely described, though their conclusions are different from those put forward by recent domestic researchers based on the theoretical analysis of bond water surrounding the clay particles. Few unpublished test results further proving that the effective stress principle is valid in clay are presented, and the view that over estimation of the volume of bond water and over emphasis of the role played by bond water surrounding the clay particles may result in incorrect conclusion is put forward. And another reason is that young researchers don’t pay much attention to the early publications.