Abstract: It is limited for existing PH foam mixer in the fixed fire prevention system of oil tank farm because its discharge pressure must be zero or minus, as a results the level of fire tank is lower than that of fire pumps between the fire pump and fire tank, it is difficult to prime, easy to suck in minus, hard to keep normal operation. In the paper taken Linyuan pump station as an example the vacuum priming was applied to resolve the problem, it is proved the operation reqirement was reached, the benifit was significant through field tests for pump priming and startup.