The present invention relates to a ring loose-leaf binder mechanism for fixing paper for a loose-leaf notebook. Said mechanism includes a rigid thin-long plate with longidutinal oxis, an articulated plate which is supported by the said rigid thin-long plate and can be pivoted about said plate and ring elements which are respectively mounted on the articulated plate and can be moved between one closing position and one opening position. Besides, it also includes a control mechanism which is supported by said thin-long plate, and can be used for controlling the above-mentioned articulated plateto make it be pivoted, and can be used for moving ring elements, and also has an operation strip and a spring.