Abstract: A nested numerical model is designed by constructing a 2.5 °(lat.)×2.5°(long.) fine grid model upon a 5°×5°P-σ 5-layer primitive equations ver-sion.Used to simulate the Somali low-level jet,the improved model shows great impact of its horizontal resolution on the jet simulation,which is 13m/s at maximum on the axis,close to the reality.Initializing with zonal mean for June,the wind field is put to a 10-day integration. With respect to the temporal fluctuations of the speed,the evolution of the jet is cut into three stages of generation,intensification and maintenance,which receive detailed discussion in terms of each of the flow fields and the compositional characteristics concerned. Just contrary to the low-level jet along the Somali coast,flows above it head south at both 500hPa and 300hPa levels. How the northward-going jet develops is also examined in a controlled test.