The invention discloses a bevel protractor used for field crop lodging studying. The bevel protractor is structurally characterized in that the bevel protractor is mainly composed of a fixed ruler, a movable ruler, a connection ruler and a fixed sleeve; length scales are arranged on the fixed ruler so that the canopy height of a crop group to be measured can be measured directly and the fixed ruler is used as a reference object during crop lodging angle measuring; a V-shaped groove is formed in the connection ruler in the long axis direction of the connection ruler, the angle values from 0 degree to 90 degrees are carved at the upper half portion of the connection ruler, and the crop group stalk lodging angle is measured according to the angle formed between the fixed ruler and the movable ruler when the movable ruler slides along the V-shaped groove of the connection ruler. When the bevel protractor is used independently or in cooperation with a crop anti-lodging strength tester, measuring of the canopy height of the crop group, the field crop lodging angle and the crop stalk lodging angle during crop anti-lodging strength measuring can be realized.