The invention discloses a cress seed selecting method, which comprises the following steps of: first, sifting harvested cress seeds to remove tiny and thick impurities, mixing the seeds with river sand for one month, and separating the seeds from the sand through water; floating the separated seeds for one or two days, and airing the seeds taken out of water; grading the aired seeds by winnowing, and simultaneously, removing part of impurities and seeds with poor quality; and finally, manually pressing the seeds which are classified by winnowing to further remove impurities. The method adopts the procedures of storing with san, floating on water and pressing and combines traditional methods of sifting and winnowing. Therefore, not only are the cress seeds selected effectively, but also the way of storing seeds in sand is added to the selection process of the cress seeds. In this way, two effects are realized because the seed selection and the relieve of seed dormancy can be finished in a combined way, and a large quantity of cress seeds can be selected within a short time. The method overcomes the difficulty of heavy workload in a traditional way of selecting seeds manually, and can be used for realizing the goal of breeding cress seeds in an industrialized way.