To address the problem that the mutual coupling effect between tags has different effects on tags at different positions, which makes the overall performance of the linear array distributed RFID system show nonlinear changes with the change of tag spacing and number. The method involves that based on the working principle of RFID and the theory of electromagnetic wave propagation, the expressions of the mutual impedance and power transmission coefficient of tags in the multitag RFID system are derived. Using power transmission coefficient, the influence of mutual coupling effect the tags at different positions and the overall performance of the system in the case of linear equidistant distribution of tags is analyzed. A mathematical model of the system's minimum power transmission coefficient changing with the tag spacing and the number of tags is established. In an open indoor environment, the response signal power is tested when the tag spacing and number change. Theoretical analysis and experimental results show that when the tags are linearly equidistantly distributed, the power transmission coefficient of the tags is nonlinearly related to the spacing. The influence of the mutual coupling effect on the tags no longer decreases monotonically with the increase of distance, but gradually decreases with the wavelength as the period, and reaches the maximum value when the spacing is a multiple of the wavelength. The location of the system's minimum power transmission coefficient fluctuates between the center and the outside with a wavelength as the spacing increases. The test results of system performance are consistent with the change pattern of the established model.