The invention provides an autonomous subsea barrier fluid system for a subsea pressure booster, the subsea pressure booster comprising a process fluid compartment, a motor compartment and a rotor assembly extending from the motor compartment into the process fluid compartment with one or several shaft seals separating the process fluid from the barrier fluid in the motor compartment. The subsea barrier fluid system is distinguished in that it comprises: a subsea barrier fluid pump, a barrier fluid delivery line, arranged between the barrier fluid pump and the motor compartment, a pressure controlled regulator, operatively arranged to at least one of the barrier fluid delivery line and the subsea barrier fluid pump, a subsea barrier fluid storage, and a barrier fluid suction line arranged from the subsea barrier fluid storage to the subsea barrier fluid pump.