Crystalline form of acetylcholinesterase inhibitor and preparation method therefor and application thereof

A crystalline form of a compound of formula I, wherein the crystalline form is selected from the group consisting of:

• Form A, Form B and Form C,
• wherein Form A has an X-ray powder diffraction pattern with characteristic peaks at three or more 2θ values selected from the group consisting of 14.914±0.2°, 15.593±0.2°, 17.617±0.2°, 18.022±0.2°, 19.525±0.2°, and 20.806±0.2°;
• Form B has an X-ray powder diffraction pattern with characteristic peaks at three or more 2θ values selected from the group consisting of 6.004±0.2°, 14.927±0.2°, 16.551±0.2°, 20.503±0.2° and 21.967±0.2°;
• and
• Form C has an X-ray powder diffraction pattern with characteristic peaks at three or more 2θ values selected from the group consisting of 15.473±0.2°, 15.832±0.2°, 18.459±0.2°, 18.824±0.2°, 20.864±0.2°, 22.331±0.2°, and 24.374±0.2°.