Technical parameter design is an effective approach to improve marine environment sounding capability for fully polarimetric synthetie apertuer radar (SAR). By analyzing geophysical contact between noise-equated backscattering coefficient and marine environment sounding, and that between radiometric resolution and marine environment sounding, we present the key technical parameters design method for fully polarimetric SAR. We first calculate radar backscattering coefficient in different marine environments by using the fully polarimetric ocean surface scattering model, and accordingly determine the noise-equated backscattering coefficient of fully polarimetric SAR ocean sounding. Then the noise-equated backscattering coefficient is used as an input parameter in SAR equation, and the function relationship between radiometric resolution and signal to noise ratio is used as a constraint condition, we thus can carry out technical parameter design, such as for signal to noise ratio, radiometric resolution and system power aperture product. By simulation calculation of fully polarimetric ocean surface scattering, we find that the noise-equated backscattering coefficient of ocean sounding is designed to -35.0 dB, which can meet the needs of fully polarimetric SAR sounding in different marine environments. Studying the function relationship between radiometric resolution and signal to noise ratio, we find that the optimal signal to noise ratio of ocean sounding is 8.0 dB. Results of C-band airborne fully polarimetric SAR design show that the above method can make technical parameter of fully polarimetric SAR meet both the need for marine environment application and system design, because of taking into account the needs of marine environment sounding.