The properties of the outermost part of normal Type Ia supernovae (SNe Ia)ejecta are studied by modeling 6 pre-maximum optical spectrawith 1D and 3D Monte-Carlo spectrum synthesis codes.At these phases, SNe with a rapidly evolving SiII 6355 line velocity(HVG SNe, 3 samples) are characterized by a low photospheric temperature.In these SNe, Si is present in the high velocity outer layers(v > 20,000 km/s). On the other hand, SNe Ia whose SiII 6355line velocity is low and evolves slowly with time (LVG SNe, 3 samples)are characterized by a higher temperature.The temperature difference stems from a different photospheric velocity,since the SNe have comparable luminosity.The CII line is marginally detected at the photosphere in 3 LVG,suggesting that burning does not proceed to the outermost layers in LVG.CaII high velocity lines (v > 20,000 km/s) are seen both in HVG and LVG.The distribution of their strength is studied by a 3D spectrum synthesis code.