In the view of fixed spacing and poor adaptability of the existing seedling needle，and the difficulty of ensuring the on-demand adjustment to adapt to different plugs of seedlings in the transplanting process，a needle-type seeding end-effector with adjustable insertion pitch was designed. The actuator was driven by a DC electric push rod，and the seedling needle was inserted obliquely along the four corners of the root. The adjustment of spacing among the needles was achieved by changing the position of the slider and the needle holder on the bracket. The seedlings of cabbages plugs were studied，namely 72，128 and 200 points. The effects of seedling age on the formation of root mites and the growth of cabbage seedlings were studied. The main structural parameters of the end-effector were determined，and the force analysis was carried out on the taking seedling. Under the premise that the roots were formed，single factor simulation was conducted for the seedling picking by EDEM. The specifications of plugs，the acceleration of seedling picking，the insertion ratio of the needle and the moisture content of root were regarded as the test factors. The root integrity rate and the failure rate of the seedling picking were regarded as evaluation indexes. Using L9(34) orthogonal test to investigate the influence of test factors on evaluation indexes. Through the range analysis，variance analysis and comprehensive weighting method，the primary and secondary influence of factors on the indexes were obtained as the acceleration of seedling picking，the moisture content of root，the specifications of plug，and the insertion ratio. The preferred parameter combinations were obtained as the acceleration of seedling picking was 0.1m/s2，the moisture content of root was 56.2%，the specification of plugs was 128 and the insertion ratio was 15%. At this time，the root integrity rate was 97.93%. The failure rate of the seedling picking was 0.81%.