Aimed at the problems that the existing air combat situation assessment model is lack of the overall performance analysis of fighters, this paper references the superiority function, takes the feature of threedimensional space into consideration, and improves combat power field model. The model of combat power field is constructed in aspects of attack, detection, maneuverability, countermeasure and alert.Based on the existing model, based on the change of equipment, the attack ability is calculated based on the situational advantage function. Change radar system coefficient, reflect the multitavget tracking abitity of modern radar. Increasing the consideration of radar lower visual ability highlights the 3D space characteristics. The paper restructures the function of combat power field based on the existing model and the change of equipment. The combat power field theory is applied in analysis of situation assessment and operations guidance. The paper verifies the effectiveness of the model. The result of research shows that threedimensional combat power field can reflect the air combat situation visually and bring the basis to maneuvering decision.