Automatic transplanting of strawberry plug seedlings is difficult since both the plant and root lumps are much bigger and their arches must be kept outward when they are inserted into the soil and root. The inserting forces and extraction forces were tested, then a novel test of constrained extraction and the root lump rupture were designed and carried out. It was found that the inserting forces were related to speed, depth and moisture content, and the maximum inserting forces were 21.47N and 57.09N when the inserting depths were 50mm and 100mm, respectively. The maximum extraction force was 9.64N, while the constrained extraction forces reached 10.85N and 42.5N when the fingers sliding displacements were 20mm and 40mm, respectively, but big sliding displacement was not ideal for transplanting precisely. Based on physical and mechanical characteristics of strawberry plug seedlings got from the above tests, an endeffector for automatic transplanting was developed. The endeffector was composed of two grippers and one arch reversing mechanism. The gripper had two doubleneedle fingers and the inserting angle was fixed, which was helpful to realize large inserting depth in limited mechanism dimensions and avoid bruise and tearing of plants and root lumps, respectively. Taking reducing of gripper width and swing range of connecting rod as dual objectives, optimal mechanism parameters of the gripper were obtained by performing linear programming. The arch reversing mechanism transformed distance between seedlings form picking to placing and changed the arch orientation simultaneously with cooperated limit switches and electromagnets. The experiments showed that the successful rates of extraction and nondamage picking were above 93% and 90%, respectively, when the picking acceleration was no more than 020m/s2. Otherwise，larger picking acceleration may lead to root lumps broken and fingers slid out. It was found that the arch reversing mechanism was able to transform distance between seedlings and change the arch orientation precisely. Finally, all seedlings were inserted into prepunched holes successfully and depth and upright degree were qualified, and survival rate reached 100% after 10d of transplanting. This novel endeffector was proved to be able to satisfy the need of automatic transplanting of strawberry plug seedlings.