The invention discloses an airplane filler cap opening mechanism which comprises an ejector rod, a limiting corner plate connected with an airplane body frame, and a pre-tightening mechanism. The airplane filler cap opening mechanism is characterized in that a boss is arranged on the middle-upper portion of the ejector rod, the upper end of the ejector rod penetrates through the limiting corner plate, and the ejector rod is limited by the limiting corner plate. The pre-tightening mechanism comprises a spring and an adjusting sleeve, wherein the adjusting sleeve is connected with an airplane body bottom plate, and the portion between the boss of the ejector rod and the adjusting sleeve is sleeved with the spring. The airplane filler cap opening mechanism is simple in structure, low in failure rate and convenient to realize; the spring and the ejector rod are adopted as the main body of the opening mechanism, the opening torque of the ejector rod is adjusted through the adjusting sleeve, and with airplane filler cap restraint states as control conditions, work can be achieved without an extra complex control system.