Proposed is a turbine vane platform sealing assembly in which compressed air is prevented from leaking to a turbine vane to improve power generation efficiency. The turbine vane platform sealing assembly includes a first sealing member inserted into a first groove formed in a turbine vane platform in a first direction, the first sealing member extending in the first direction, a second sealing member inserted into a second groove formed in a second direction intersecting the first direction of the turbine vane platform, with an end part of the second sealing member being in contact with an upper surface of the first sealing member, and the third sealing member having a portion formed by extending in the first direction and a remaining portion formed by bending in the second direction at a bend line at which the first sealing member and the second sealing member contact.