A slow closure system for toilet covers comprising at least one main shell, into which pre-determined fluid having certain viscosity is added; at least one shaft shell, which is placed in said main shell, one side of which has such a width that it makes contact with the inner surface (A') of said shell, the other side of which is much narrower than its side contacting the inner surface (A') of the main shell; at least four lateral wall (9, 9'), which are provided on the shaft shell so as to stand as corresponding couples; at least one shaft comprising at least two channels, which are formed by said corresponding lateral walls (9, 9') wherein the slow closure system further comprises - at least one hole provided on each of the corresponding two lateral walls (9, 9') and positioned so as not to be concentric with each other; - at least one plate part, which is placed in each of said channels, which has at least one hole concentric with the hole on one of the corresponding lateral walls (9, 9'), which leans on the lateral wall comprising the hole concentric with the hole on it in one of the channels in closed position of the cover, which has the hole not concentric with the hole with the hole on it in other channel; - at least two projections, which extend from the inner surface (A') of the shell towards the inside of the shell and which make contact with said lateral walls having the hole concentric with the plate part on the corresponding lateral walls (9, 9') on the shaft shell while the cover is in the closed position; - at least one space, which is provided on the shaft shell and controls fluid passage according to position of the said projection, the depth of which increases from its one side towards its other side; - at least one hole on each of the lateral walls (9, 9') comprising the hole concentric with said plate part; - at least one chamber, which is formed between one of said projections and one of the corresponding lateral walls (9, 9') on the shaft shell while the cover is in the closed position; - another chamber, which is formed during opening of the cover between said projection and the lateral wall contacting with the projection. - at least one hole provided on each of the corresponding two lateral walls (9, 9') and positioned so as not to be concentric with each other; - at least one plate part, which is placed in each of said channels, which has at least one hole concentric with the hole on one of the corresponding lateral walls (9, 9'), which leans on the lateral wall comprising the hole concentric with the hole on it in one of the channels in closed position of the cover, which has the hole not concentric with the hole with the hole on it in other channel; - at least two projections, which extend from the inner surface (A') of the shell towards the inside of the shell and which make contact with said lateral walls having the hole concentric with the plate part on the corresponding lateral walls (9, 9') on the shaft shell while the cover is in the closed position; - at least one space, which is provided on the shaft shell and controls fluid passage according to position of the said projection, the depth of which increases from its one side towards its other side; - at least one hole on each of the lateral walls (9, 9') comprising the hole concentric with said plate part; - at least one chamber, which is formed between one of said projections and one of the corresponding lateral walls (9, 9') on the shaft shell while the cover is in the closed position; - another chamber, which is formed during opening of the cover between said projection and the lateral wall contacting with the projection.