For civil aircraft with engine wing mounts, the flap structure is located within the range of engine jet flow. The composite honeycomb sandwich typical structure in the flap is subjected to combined thermal-acoustic-static pressure loads, facing severe structural integrity issues. This paper reviews the load environment of the flap structure and establishes a set of thermal-acoustic-static pressure combined loading test equipment for composite honeycomb sandwich typical structures. Based on this test equipment, a combined loading test of 158 dB noise, −0.045 MPa negative pressure, and 80 °C temperature was conducted on the composite honeycomb sandwich typical structure. The dynamic strain and acceleration response characteristics of the composite honeycomb sandwich typical structure under various working conditions were measured. The test results show that superimposing negative pressure and high temperature on the acoustic load reduces the peak response frequency of the test specimen, increases the response value, and adversely affects the structural strength.