In this paper,the knot resonator-coupled microfiber Mach-Zehnder interferomete r (MZI) is proposed,and the dependence of temperature and salinity sensitivities on its structure parameters is calculated.The transmission spectra at different temperatures and salinities are calculated, and the resonant dip and the interference dip appear together in the spect ra,resulting from resonance and interference,respectively.The resonant dip an d interference dip have different responses to the changes of temperature and salinity,and thus can be used to simultaneously measure temperature and salinity of seawater.Resu lts show that the sensitivity of resonant dip is only related to the microfiber diameter of knot resonator,while the sensitivity of interference dip is related to the two microfiber diameters and lengths of MZI. When the microfiber fabricating the knot resonator is the thinner and longe r one between the two microfibers of MZI,high sensitivities can be obtained.Compared with traditional fiber Bragg gratings,the temperature and salinities sensitivity of i nterference dip improve by 75times and about 3650times after optimizati on,respectively.The proposed interferometer shows the advantages of simple structure and high sensitivity, and may offer theoretical basis for development of marine microfiber sensors.