This paper analyses the popular design method for the perpendicular curve on airfield vertical section ,points out its defects , and also designates that current method to estimate sight distance can not solve the sight distance problem of vertical section with part concave or setting perpendicula curve. So , it suggests two innovated methods to design the perpendicular curve. At last , a new method to estimate sight distance is brought forward , and this method is strong and easy in computer program.