Authors have developed a technique called the cement-mixing and mechanical dehydration method (CMD) as one of recycling techniques for soft clay slurry. In the CMD procedure, soft clay mixed with cement is dehydrated with a high dehydration pressure for the purpose of increasing the strength. In order to develop the effective procedure of the CMD for achieving a high strength with a low dehydration pressure, the effect of controlling soil grains on the strength of clay produced by the CMD was investigated in this paper. The following conclusions are obtained: (1) The dehydration time required completing consolidation process decreases with increasing sand content. Therefore, mixing sand content into the cement-mixed and dehydrated specimen is effective for shortening dehydration time and increasing specimen dimension in the future development for the CMD. (2) The unconfined compressive strength of clay produced by the CMD is a unique function of the water-cement ratio and therefore it is possible to obtain a high strength specimen by decreasing water-cement ratio. (3)Based on the principal component analysis and the multiple linear regression analysis, a formula to estimate the unconfined compressive strength of clay produced by the CMD is proposed using the clay content, dry density and water-cement ratio.