Abstract: Equivalence of the two kinds of liquid limit test method-Casagrande method and Cone method, is discussed, The concept of "average equivalent penetration" is clarified with definite physical significance. On the basis of the summary of the L. L. and P. L. comparative tests, some problems as the determination of the heqv1 the undrained strength of remould soils at L. L., and the application of some statistical methods, are explained. Some defects in the summary mentioned above are corrected. 76 g cone, (30 apex angle) 17mm penetration L. L. of the cone method is equivalent to the L. L. according to ASTM standard, is concluded and reconfirmed.