An extensible curtain rail includes a rail main body, more than one connection seat and a decorative panel. The decorative panel and the rail main body are assembled and connected with each other by means of the connection seat. The connection seat can be inward contracted or outward extended to adjust the gap between the decorative panel and the rail main body in accordance with different sizes of curtain assemblies to facilitate installation thereof. The decorative panel is detachable from the rail main body to provide larger installation space and more quickly install the curtain assembly.