To reduce the injure of seedlings caused by pulling during transplantation, mechanic properties were analyzed in the process of pulling of floating seedlings of cotton, and a mechanics model for pulling up seedlings was established. Through mechanic analyzing and calculating, it was found out that the angle for pulling and the clamping position on the seedlings were the main factors that affect the pulling force, the length of broken roots and the weight of matrix fallen off. And the test results showed that the best way for pulling seedlings involves angle α=0° and clamping position s=0, under which the pulling force, the length of broken roots and the weight of matrix fallen off were all the smallest, which caused minimal damage to cotton seedling.