Accurately obtaining the vibration environment of aircraft structures and onboard equipment is crucial. Traditional vibration environment prediction methods have low accuracy and may lead to issues of over or under testing in later vibration environment tests. An innovative vibration environment prediction method based on Extended Operating Condition Transfer Path Analysis (OPAX) was proposed. A vibration environment prediction model was constructed using measured data, and then the model was used to predict the vibration environment under new operating conditions. In the laboratory environment, a vibration testing system for a typical equipment compartment of a certain type of aircraft was built, and a vibration environment prediction model for airborne equipment was built based on the OPAX method, and its prediction accuracy was verified. Comparing the expected results with the experimental results, it was found that: ① the error between the predicted root mean square value of the model under new operating conditions and the root mean square value of the experimental test remained within 20%; ② Within the expected frequency range, the expected change trend of the model under new operating conditions is basically consistent with experimental testing, with significant differences at individual frequencies. Based on the predicted results under new working conditions, this vibration environment prediction method based on OPAX has high prediction accuracy, requires less data to build the model, is convenient to build, and has operability and practical engineering value.