This paper combined subjective questionnaire and objective mental task to evaluate cabin air quality. In the experiment, subjective questionnaire and mental arithmetic tasks were combined in a simulative short flight in the 7-row cabin mockup to study cabin air quality, aiming at obtaining mass data of human’s intuitive feeling and reaction. As is known to all, subjective questionnaire sometimes fails to reflect the human feeling, and there is also a lot of uncertainty. Mental arithmetic tasks can compensate for the lack of it to some extent. The correct rate of the arithmetic tasks can reflect people’s reaction rate, and further reflect the human sense of air quality. For example, with the carbon dioxide concentration increasing, the correct rate decreases. In the experiment, we also use the simplest mental task method called “count money”. The comparison of the two methods will also be made. The gray relational degree is also calculated about the air quality influence the symptoms. The objective is to evaluate the air quality by subjective questionnaires and mental arithmetic task results, and finally lay the foundation of improving cabin air quality.