This article considers the output‐feedback control problem for a class of stochastic high‐order nonlinear systems with time‐varying powers. In the control design process, by choosing proper upper and lower bounds for time‐varying powers, a state observer is constructed to estimate the unmeasured states. With the help of the adding a power integrator technique, the backstepping technique, and homogeneous domination design method, an output‐feedback control scheme is designed. The closed‐loop systems can be proved to be globally asymptotically stable in probability. Finally, the efficiency of the presented control method is verified by a simulation example.