Objective: The study of fire spread behavior in wires holds significant importance for guiding fire safety measures in variable pressure environments such as nuclear power plants, aerospace applications, hyperbaric oxygen chambers, and high-altitude areas. Currently, there is a lack of comprehensive research focused on variable pressure environments widely applied in spacecraft, high-altitude regions, nuclear power plants, and civilian hyperbaric oxygen chambers. Therefore, this study investigates the fire spread and molten droplet behavior of polyethylene (PE) wires under variable pressure conditions ranging from 40 to 500kPa using a self-built experimental platform. Methods: This study selected typical thermoplastic PE wires as the research subject and constructed a fire spread experimental platform to investigate the effects of variable pressure conditions (40-500kPa) and oxygen volume fractions of 21% and 30% on fire spread behavior. Simulations were conducted using the solidification/melting model in Fluent software to analyze the melting and dynamic motion of molten material suspended on a metal plate. Results: 1) Within the 40-100kPa range, a low-luminosity blue flame appears at the base of the flame and fades as pressure increases. For an oxygen volume fraction of 21%, the bottom blue flame disappears after 100kPa. For a 30% oxygen volume fraction, it vanishes at 60kPa. At pressures from 100kPa to 500 kPa, the blue region at the bottom of the flame disappears, flame brightness intensifies. The top flame color changes from bright yellow to orange, and soot production increases. Increasing the oxygen volume fraction from 21% to 30% reduces the orange region at the flame's top and decreases black soot in the upper section, reshaping the flame into a more triangular form. During this stage, the fire spread rate and mass loss rate increase significantly; 2) As pressure increases, the flame width of the PE wire decreases. At 500kPa, the flame width measures 2.0 and 2.2cm for oxygen volume fractions of 21% and 30%, respectively. Flame height increases with pressure, peaking at 500kPa. At oxygen volume fractions of 21% and 30%, the maximum flame heights are 3.7 and 4.8cm, respectively; 3) At an oxygen volume fraction of 21%, molten dripping occurs in the 40-80kPa range. However, at an oxygen volume fraction of 30%, molten dripping ceases above 60kPa. Simulations reveal that molten droplets form 4.4s after PE is heated and separate from the main body under gravity with a maximum velocity of approximately 22cm/s. Surrounding airflow exhibits a spiral motion during droplet detachment. Conclusions: This study primarily reveals the fire spread and molten droplet behavior of PE wires under different pressure conditions, providing a foundation for predicting and preventing fire development in PE wires found in variable pressure environments.