In order to obtain a spatial planetary gear train with higher transmission ratio, which can shorten the large horizontal offset of picking seeding trajectory, a kind of special shaped non-circular bevel gears based on spherical curve was put forward, and a wide-narrow distance transplanting mechanism composed of special shaped non-circular bevel gears and crossed cylindrical gears was obtained. The pitch curve of special shaped non-circular bevel gears was designed by two non-uniform B-splines which had continuous angles and discontinuous radius. The gear pair could continuously and smoothly work after adjusting the height of tooth profile curve in the transition section of two non-uniform B-splines. The theoretical model of wide-narrow distance transplanting mechanism was built up. An optimization program was finished, and the effect of the different shape of special shaped non-circular bevel gears to the widenarrow distance planting trajectory was analyzed. A three-dimensional model was built up by computer, and an actual physical model was processed. The shapes and speeds of the planting trajectory which formed by the two models were compared, and the values of measuring parameters were almost the same. A test with seeding by transplanting mechanism was carried out based on rotary trial soil bin. Speed comparison between the transplanting mechanism composed of special shaped non-circular bevel gears and transplanting mechanism composed of non-circular bevel gears was made, and the result showed that the wide-narrow distance transplanting mechanism composed of special shaped non-circular bevel gears had the advantages in shortening the large horizontal offset of picking seeding trajectory, and the planting trajectory was better.