Abstract: To meet the demand by steel tube makers for pressure testing of large-sized steel tubes,a 40 MN hydrostatic testing line for large-sized straight welded tubes is development-designed by Taiyuan Heavy-duty Machinery Corp.,Ltd. The testing line features high test pressure,broad size range and quick operation cycle. Briefed here are the equipment composition,main technical data and testing process flow of the line. Focused on are the equipment configuration,data design and design characteristics of the liquid system as an integrated part of the hydrostatic testing line.