Abstract: By using visual tracing techniques, real-time digital process techniques and non-target measuring techniques,the lab model tests on base soil-filter of broadly graded sandy soil were carried out. The applicability of the filter-layer standard has been discussed; different filter layer thickness and compression rate on piping development influence has invested. The resuits proved that: the traditional Terzaghi filter guideline is improper for broadl graded sand, d₈₅ of moving particles can be used in the design guideline; Increasing filter layer thickness could improve that the system of the seepage failure, but the system penetration ability only improved a little; hydraulic gradient increases faster is not conducive to the stability of the system.