Abstract: The present invention relates to B24B, and more specifically, the present invention relates to an endpoint detection window, a chemical mechanical polishing pad with a window and a preparation method thereof. A side surface of the window is provided with a plurality of circumferential grooves. In the present invention, a column-shaped window with a specially designed side surface structure is provided and subjected to integrated pouring and molding with a polishing pad to manufacture a chemical mechanical polishing pad having high bonding strength between the window and the polishing pad. As a side surface of the window is of a multi-groove structure, not only is the bonding contact area between the window and the pad increased, but also a convex structure is formed by a polishing pad body material poured into the grooves so as to form an embedded bonding manner with a groove structure of a window material.