A self-standing liquid package bag provided with flat film valve is provided at a single use form by self-standing a liquid package bag with a film valve having a one-way function without being required to house and fix in another outer package vessel and obstructing the one-way function of the film valve. The self-standing liquid package bag of the invention is formed by protrudingly disposing a flat film valve having a one-way function, which is subjected to a wetting treatment at full inner faces in a pouring path and a portion adjacent to a fused part near to the pouring path, on an upper part or top part of at least one side edge of a bag body portion and disposing a self-standable bottom portion at bottom thereof.