The quality of civil aircraft pitching moment characteristics affects the stall angle and the maximum coefficient of lift. It plays an important role in aircraft‵s safety and economy performance. Aircraft maneuverability/stability and stall characteristics are strictly required by design specifications and airworthiness standards home and abroad. This paper gave a theoretical deduction of the allowable 'pitch up' magnitude and analyzed the cause of 'pitch up' by wind tunnel data. The results show that to meet the airworthiness requirements of deceleration rate and positive stick force, 'pitch up' is allowed but the magnitude is restricted. The decrease of local dynamic pressure of horizontal tail makes the pitching moment contribution decrease. The decrease of pitching moment contribution of horizontal tail is the primary cause to 'pitch up'.