Abstract: Borehole strainmeter is used to measure crustal rock strain, which can be divided into two types: volumetric strainmeter and component strainmeter. The former is used for Volumetric strain observation, and one of the latter functions is to measure area strain. A large number of observations show that the effect of air pressure on the two is significant and continuous. Therefore, it is necessary to establish the corresponding mechanical model, to solve the pressure influence coefficient and to explore the law of change. It is of practical significance to the correct analysis of the background field of earthquake precursor observation. Therefore, it is necessary to establish the corresponding mechanical model, to solve the pressure influence coefficient and to explore the law of change. It is of practical significance to the correct analysis of the background field of earthquake precursor observation. According to the stress wave stress solution given by Fung, the concept and demarcation point of long and short periodic pressure wave are defined, and the elastic response equation of the volumetric strain and area strain to the periodic pressure wave are derived by combining the existing borehole strain observation model, the theoretical solution of the influence coefficient of air pressure is given,and the relationship and difference between the two are analyzed, and the pressure coefficient of the volumetric strain theory is compared with the measured values of some stations in Beijing, Tianjin, Hebei, Shandong and other regions. The results show that the two sets of curves are basically consistent, and the correctness and reliability of the model are preliminarily verified.