The no-sand vacuum preloading technique is proved unsatisfactory for improving the newly-reclaimed mud foundation,so we analyze the reasons from both objective factors and subjective factors.The result reveals that ：1) The physical characteristics and permeability coefficient of newly-reclaimed mud are the objective factors,which lead to the difficulty of vacuum drainage consolidation and serious barriers with low permeability around the PVDs during vacuum preloading,and thus result in unsatisfactory improving effect.2) The performances of PVDs and horizontal drainage system are the objective factors.The characteristic opening size of filter stipulated in de current code is too small (O95＜0.075 mm),and the curvature of vertical drains and transfer resistance in horizontal drains are too large,these also results in the poor improving effect.3)The winding-connecting part of horizontal drainage system should be buried in filling/ fine/ medium fine/ medium coarse horizontal drainage to improve its three-dimensional permeable effect.