Petrochemical device is high, large and heavy, for which, the bearing capacity of foundation and the settlement deformation should be strictly controlled. The paper presents a petrochemical project in soft soil of Ningbo, because of the poor engineering geological conditions and large wind load, the horizontal bearing capacity is a very important factor. In order to achieve the horizontal bearing capacity parameters of pile foundation in accordance with the practical conditions, the horizontal static load test on the foundation of prefabricated square-pile is carried out under the conditions of different pile diameters, pile lengths and vertical loads on pile top in working area. The test results show that when the pile top is under the free condition, the horizontal bearing capacity of single pile increases along with the increase of diameter and the length of the pile, not being linear growth, but the power function relation. The horizontal bearing capacity of single pile increases along with the increase of vertical load on pile top, and also with power function relation. The horizontal bearing capacity of pile group is larger than the sum of that of single piles.