Let $M$ be an $n$-dimensional complete connected Riemannian manifold with sectional curvature $\operatorname{sec}(M) \geq 1$ and radius $\operatorname{rad}(M)>\pi /2$. In this article, we show that if $\operatorname{conj}(M)$, the conjugate radius of $M$, is not less than $\operatorname{rad}(M)$, then $M$ is isometric to a round sphere of constant curvature.