The method of Raman-Nath symmetric beam splitting based on magnetically insensitive states and the scheme of internal state interference are proposed. The interference based on magnetically insensitive states is insensitive to the magnetic fluctuation, which is beneficial to the contrast enhancement of interference fringes. If such a Raman-Nath symmetric beam splitting method is applied in the path-conjugate atom gyroscope, the system noise is obviously reduced. By means of optimizing the symmetric-beam-splitting parameters of double pulses, it is possible to obtain a high diffraction efficiency. The scheme of internal state interference is successfully used to solve the problem of momentum state interference being susceptible to the environment.