The three-dimensional pressure cell (3DPC) provides a novel method to measure the geostress of the deep soft surrounding rock. However, due to the installation of 3DPC, the distribution of initial stress field of the surrounding medium is inevitably changed, and then the redistributed and concentrated stress result in the significant indetermination of the relationship between the measured stress by 3DPC and the initial stress field of surrounding rock. The above problem also exists in the applications of earth pressure cell. In order to study the embedding effect of 3DPC on the initial stress field of medium and stress properties measured by 3DPC, numerical software is employed to simulate the installation process and the stress redistribution of the medium. Under different conditions of stress state and the elastic modulus ratio of 3DPC to surrounding medium, the characteristics of the principal stress redistribution field and the stress distribution of each part of 3DPC are analyzed. Moreover, the analytical models are established on the basis of the variations of measured stress by 3DPC with different initial stress state and modulus ratio. The well-fitted results show that the proposed theoretical expressions are validated to reflect the relationship between the 3DPC measured stress and the initial stress of the surrounding medium.