A valve assembly with low gas level signaling and controlling function includes a primary valve threadedly engaged with an outlet of a tank, the primary valve being formed with a recess in which is fitted a plunger having an upper end extending upwardly through the primary valve to engage with a knob, a low level linking device comprising a tubular tube connected with a bottom of the primary valve, a flexible rod having an end extending upwardly through the tubular tube to connect with the primary valve and another end connected with an end of a float rod, and a float connected with another end of the float rod, and a release rod connected a pusher which is operatively connected with the primary valve so that when the release rod is turned, the pusher will move down the flexible rod to open the primary valve, whereby the valve assembly can detect the amount of gas remaining in a gas tank and will close when the level has decreased to a certain level thereby alerting the users and enabling them to replenish their gas supplies before all gas has been exhausted in the present gas tank, and in the meantime the user may use a release valve to release the closed valve and use the remaining gas.