For the design of earth structures on soft clay deposits, it is a foundamental problem to evaluate the strength of the ground correctly. The undrained strength of soft clay deposits is determined by the half of the mean unconfined compressive strength qu in Japan. Although this qu method has been used in practical design works for more than 30 years, there are still some important problems to be solved. One problem is that the validity of the qu method highly depends on the quality of undisturbedsoil sample, while there exists no accepted method to evaluate the sample quality. For this reason, there are some criticisms to use of qu among the professions in the international geotechnical society. In this report, the back-grounds of qu method are presented at first. Comparing the strength of qumethod with those from the field vane shear tests, SHANSEP method and Recompression method,detailed discussions on the effectiveness are made, and finally a newly proposed Advanced qu method, in which the quality of sample and the reasonable undrained strength can be evaluate at the same time, is introduced and the applications are presented.