Researching flow in aspirating lines in altiplano environment can offer gist of designing air aspirating lines of HSASD (High Sensitivity Aspirating Smoke Detector)at tableland. Velocity equation of air aspirating line and velocity equation of aspirating aperture could be derived from continuity equation and dynamics equation. Average velocity of air aspirating line and average velocit y of aspirating aperture could be concluded when air aspirating line had only single aspirating aperture. Contrasting average velocity of air aspirating line and aspirating aperture at high altitude and normal atmosphere pressure concluded difference of them and main factors that affected flow of air aspirating lines at high altitude. Flow velocity of air aspirating lines and aspirating aperture is mainly affected by viscosity coefficient, negative pressure at aspirating pump inlet. Equal flow velocity of air aspirating lines and aspirating aperture can be got through shortening aspirating lines length. Equation 4.14 gives a compute method of shortening aspirating lines length in altiplano environment.