In order to demonstrate effectiveness of vibratory probe compaction at silt deposit, a self-developed vibratory probe with cross section and compaction equipment were adopted to treat silt deposit at Suqian-Xinyi Expressway liquefiable site in China. Field pilot tests were conducted to study spatial variation of compaction effect. It is shown that strength increase at vibration point is largest after ground improvement, while a small increase occured at 1m, but not 2m from vibration point. The radial influence range and effective reinforcement radius are 2m and 1m. The largest settlement is in a zone within a radius about twice the probe diameter. The major settlement occurred immediately after compaction, slightly increased with time.