A connective device in a partition and screen system comprises at least and upright post, a plurality of retaining pins, a plurality of trunking parts longitudinal, and at least a partition. The upright post is cylindrical with a homogeneous cross section with longitudinal slide grooves circumferentially disposed through the entire length thereof. The retaining pins are selectively inserted into the slide grooves and each of the retaining pins has an arched side with two opposite lateral edges. The trunking parts are connected to the respective coupling pieces so as to be positioned next to the upper end and the lower end of the upright post. The partition fits with two of the trunking parts in a way of being disposed between one next to the upper end of the upright post and the other one next to the lower end of the upright post.