In this paper, we prove that any $��$-noncollapsed gradient steady Ricci soliton with nonnegative curvature operator and horizontally $��$-pinched Ricci curvature must be rotationally symmetric. As an application, we show that any $��$-noncollapsed gradient steady Ricci soliton $(M^n, g,f)$ with nonnegative curvature operator must be rotationally symmetric if it admits a unique equilibrium point and its scalar curvature $R(x)$ satisfies $\lim_{r(x)\rightarrow\infty}R(x)f(x)=C_0\sup_{x\in M}R(x)$ with $C_0>\frac{n-2}{2}$.

Corollary 3.11 is added