Dual polarization weather radar mainly has two operating modes: simultaneous transmission and reception; horizontal/vertical alternate transmission and simultaneous reception. Comparison is conducted on the advantages and disadvantages of the two modes in aspects of the accuracy of spectral moment estimation, the measurement range for velocity, ground clutter suppression, signal to noise ratio, and so on, and the depolarization phenomenon in weather radar as well as its effect on differential reflectivity products are analyzed. Taking linear depolarization ratio as an example, the polarization isolation degree in dual polarization weather radar is discussed. Theoretical analysis and computation indicates that accurate polarimetric measurement demands a strict polarization isolation degree.