Profiles of Hα,Hβ and Hγ lines, cmited from a TEA CO2 laser induced silane plasma, are measured with an optical multichannel analizer (OMA Ⅲ) The experimental results show that FWHM (full width of half maximum) of the three lines increases with the main quantum number of the corresponding upper level of the transiti ons, i.e. △λ1/2(Hα)1/2(Hβ)1/2(Hγ), this suggests that the dominant broadening mechanism of the lines is Stark broadening. Fitting the measured Hα profile to theretical data of Stark broadening, two parameters of the plasma are obtained: average electron density N = 1017cm-3 and electron temperature T = 40 000 K. From time tesolved measurements of Hβ profile, a curve of electron density versus time is derived.