The utility model discloses an adjustable guide vane system for a power turbine of a gas turbine, relates to an adjustable guide vane system for a turbine, and aims to solve the problem that the conventional adjustable guide vane system for the power turbine of the gas turbine has a complex sealing structure and low operating stability. The other end of a rocker arm is connected with the upper end of a ceramic rotating shaft; a second bearing bush is arranged on an upper end face of a case; the adjustable guide vane consists of an upper guide vane shaft, a lower guide vane shaft and an adjustable guide vane main body; the upper guide vane shaft, the adjustable guide vane main body and the lower guide vane shaft are fixedly arranged into a whole in turn from top to bottom; the upper guide vane shaft is coaxial to the lower guide vane shaft; a ceramic shaft sleeve is sleeved on the upper guide vane shaft; the upper end of the upper guide vane shaft passes through the case and is fixedly connected with the ceramic rotating shaft; an end cover is fixedly arranged on an upper end face of the second bearing bush; a flexible graphite shaft sleeve is sleeved on the lower guide vane shaft; and a left half cylinder and a right half cylinder are fixedly assembled into a whole. The adjustable guide vane system for the turbine is used for adjusting the through-flow capacity of a turbine stage.