A multi-grade seed cotton heavy impurity cleaning and separating device, being mounted at an output end of a picking platform of a cotton picker. A seed cotton flow picked by the cotton picker is conveyed by means of the picking platform to the multi-grade seed cotton heavy impurity cleaning and separating device. The multi-grade seed cotton heavy impurity cleaning and separating device basically comprises a succession of elongated panels arranged in a layered structure and comprises a first-grade heavy impurity removing mechanism, a second-grade heavy impurity recycling mechanism, a third-grade heavy impurity recycling mechanism and a pipeline connecting the above three mechanisms. Said multi-grade seed cotton heavy impurity cleaning and separating device adopts multi-grade sequential cleaning, achieving a high impurity cleaning rate and a low seed cotton loss, reducing secondary impurities mixed with the seed cotton in the cleaning process, realizing graded recycling of cotton bolls and branches, reducing the cotton fiber dyed during the follow-up cotton boll processing, improving the work efficiency of an onboard seed cotton pre-processing machine.
