The sparse planting and transplanting of plug seedlings is a key step in the cultivation of seedlings in facility agriculture, which can provide an excellent growth environment for seedlings and increase production and income. Aiming at the problems of low automation degree of adjustable plant spacing equipment, inefficient manual work, vulnerable to seedling damage and injury in the process of thinning and transplanting, a plant spacing adjustable seedling end-effector was designed based on cylindrical cam, which can realize thinning and transplanting between different plant spacings. First of all, the overall structure of the end-effector was designed and its working principle was determined. Secondly, through theoretical analysis, the key parameters of the cylindrical cam and the finger were determined, and the stress condition under operation was analyzed. Thirdly, EDEM and Recur Dyn were used to establish a composite model of seeding bowl root-soil for coupling simulation single factor simulation test, and the factor range of subsequent orthogonal test was determined. Finally, a transplanting test platform for plug seedlings was built, and orthogonal tests were carried out with the seedling needle included angle, penetrating angle, seedling needle spacing and variable pitch speed as test factors, and the seeding bowl deformation quantity and the transplanting success rate as test indexes. The experimental results showed that the primary and secondary influence order of test factors on the seeding bowl deformation quantity were penetrating angle, variable pitch speed, seedling needle included angle, seedling needle spacing. And the primary and secondary influence order of test factors on the transplanting success rate were seedling needle spacing, penetrating angle, pitch change speed, seedling needle included angle. The verification test was carried out under the optimal parameter combination with seedling needle angle of 10°, penetrating angle of 4°, seedling needle spacing of 8mm, and pitch change speed of 5mm/s, and the plug seedlings were transplanted from 128cell to 72cell and from 72cell to 50cell respectively. The average seeding bowl deformation quantity of 128cell was (1.13±0.68)mm, and the average seeding bowl deformation quantity of 72cell was (1.51±0.64)mm. The total success rate of transplant was 93.33%, and the transplanting efficiency of the whole machine was 22 plants/min. It satisfied the needs of different plug tray specifications and had strong applicability. The research result can provide theoretical basis and technical support for the research of the thinning and transplanting operation device.