A telescopic curtain guide rail, comprising: an inner rail, an outer rail, and a transmission unit; wherein the inner rail is connected to a side of the outer rail, and the inner rail is embedded in the outer rail and slidable along the outer rail; and wherein the transmission unit comprises a driving wheel, a driven wheel and a conveyor belt, the driving wheel and the driven wheel are respectively located at two opposite ends of the telescopic curtain guide rail, the conveyor belt is wound on the driving wheel and the driven wheel, characterized in that the telescopic curtain guide rail comprises a guide sleeve and said guide sleeve is a hollow tubular structure with openings at both ends, and the guide sleeve is sleeved outside a connection between the outer rail and the inner rail; and in that the transmission unit further comprises a first fixed pulley and a second fixed pulley, and the driving wheel is connected with a motor; the first fixed pulley is located at one of an inner end of the inner rail and an inner end of the outer rail, and the second fixed pulley is located at the other one of the inner end of the inner rail and the inner end of the outer rail; the driving wheel and the first fixed pulley are respectively disposed on two ends of the inner rail one of which is the inner end of the inner rail, or respectively disposed on two ends of the outer rail one of which is the inner end of the outer rail; and the conveyor belt is wound on the driving wheel, the driven wheel, the second fixed pulley and the first fixed pulley; a distance between the driven wheel and the driving wheel is decreased while a distance between the first fixed pulley and the second fixed pulley is increased, when the inner rail moves towards the outer rail; or, the distance between the driven wheel and the driving wheel is increased while the distance between the first fixed pulley and the second fixed pulley is decreased, when the inner rail moves away from the outer rail. wherein the inner rail is connected to a side of the outer rail, and the inner rail is embedded in the outer rail and slidable along the outer rail; and wherein the transmission unit comprises a driving wheel, a driven wheel and a conveyor belt, the driving wheel and the driven wheel are respectively located at two opposite ends of the telescopic curtain guide rail, the conveyor belt is wound on the driving wheel and the driven wheel, characterized in that the telescopic curtain guide rail comprises a guide sleeve and said guide sleeve is a hollow tubular structure with openings at both ends, and the guide sleeve is sleeved outside a connection between the outer rail and the inner rail; and in that the transmission unit further comprises a first fixed pulley and a second fixed pulley, and the driving wheel is connected with a motor; the first fixed pulley is located at one of an inner end of the inner rail and an inner end of the outer rail, and the second fixed pulley is located at the other one of the inner end of the inner rail and the inner end of the outer rail; the driving wheel and the first fixed pulley are respectively disposed on two ends of the inner rail one of which is the inner end of the inner rail, or respectively disposed on two ends of the outer rail one of which is the inner end of the outer rail; and the conveyor belt is wound on the driving wheel, the driven wheel, the second fixed pulley and the first fixed pulley; a distance between the driven wheel and the driving wheel is decreased while a distance between the first fixed pulley and the second fixed pulley is increased, when the inner rail moves towards the outer rail; or, the distance between the driven wheel and the driving wheel is increased while the distance between the first fixed pulley and the second fixed pulley is decreased, when the inner rail moves away from the outer rail.