Abstract: Based on the Finite Volume Coast and Ocean Model (FVCOM ), a numerical model for M₂ and S₂ tidal waves in the Northern Indian Ocean (from 31^°E to 102^°E, from 16^°S to 31^°N) is established, and the characteristics of Semi-diurnal tides and tidal currents are investigated. We carried out a numerical test on the coefficient of bottom friction by using cost function gradient descent method, in which the change curve of root mean square errors (RMSE) of tidal constituent harmonic constant vector is obtained and optimal bottom friction coefficient is thus determined. Simulation results based on the optimal coefficient are compared and verified with the harmonic constants at the satellite altimeter intersection points of TOPEX/Poseidon, provided by the International Hydrographic Organization (IHO), and measured at tidal gauge stations, and the results are in good agreement with the observational data. It shows that the deviation of the simulated amplitude is from 2 cm to 4 cm and that of phase-lag is about from 7^° to 8^° whenc ompared with the T/P data; the deviation of amplitude is about from 3 cm to 6 cm and that of phase-lag is about from 8^° to 9^° when compared with the tide station data. We also analyzed M₂ and S₂ tidal propagation characteristics and spatial distribution of tidal ellipses in the region, and found that the M₂ tidal constituent has an amphidromic point in the southern Arabian Sea and two amphidromic points in the Persian Gulf, with maximum amplitude exceeding 80 cm, and the tidal current is mostly clockwise in the northwest Indian Ocean and central Bay of Bengal. The tidal current velocity is larger in the northeast of the Arabian Sea, the Andaman Sea, the Persian Gulf and the northern part of the Bay of Bengal, with maximum velocity of 160 cm/s. Tidal wave propagation characteristics, location of amphidromic point, and spatial distribution of tidal ellipse of S₂ are similar to those of M₂, but tidal wave amplitude and tidal current velocity of S₂ are relatively smaller than those of M₂.