Abstract: The settlement of the foundation on the soft ground would affect the normal operation and safety of the substation. The existing reinforcing methods and machinery can't work in the high-voltage fields. For a 220kV substation on the sea sediment foundation in a city along the coast, Jiangsu Province, China, the settlement should be controlled at a 2.2m high security restrictions with the requirement of the original operation of the substation. A small-scale pile-driver was developed, and reinforcement tests were carried out. The results show that the small-scale pile driver can work well for running substation, which is a breakthrough of the reinforcement of substation foundation at the restricted space. The micro-steel pipe pile can effectively prevent the settlement of independent foundation.The technology of prestressing on the pile top, soldering after withstand, can improve reinforcement effect.