We show that on a compact locally conformal K$ddot{a}$hler manifold $M^{2n}$ (dim $M^{2n};=;2n;{geq};4$), $M^{2n}$ is K$ddot{a}$hler if and only if its conformal scalar curvature k is not smaller than the scalar curvature s of $M^{2n}$ everywhere. As a consequence, if a compact locally conformal K$ddot{a}$hler manifold $M^{2n}$ is both conformally flat and scalar flat, then $M^{2n}$ is K$ddot{a}$hler. In contrast with the compact case, we show that there exists a locally conformal K$ddot{a}$hler manifold with k equal to s, which is not K$ddot{a}$hler.