<p style='text-indent:20px;'>Linear complementary dual (LCD) codes play an important role in data storage, communications systems and cryptography. In this paper, we construct some symplectic LCD codes from quasi-cyclic (QC) codes, and prove that these symplectic LCD codes with dimension two over <inline-formula><tex-math id="M1">\begin{document}$ \mathbb{F}_{2^a} $\end{document}</tex-math></inline-formula> are maximum-distance-separable (MDS) codes. By extending the generator matrices of symplectic LCD MDS codes with dimension two, we obtain a series of symplectic LCD codes over <inline-formula><tex-math id="M2">\begin{document}$ \mathbb{F}_{2^a} $\end{document}</tex-math></inline-formula>. As an application, some new entanglement-assisted quantum error-correcting codes (EAQECCs) over <inline-formula><tex-math id="M3">\begin{document}$ \mathbb{F}_{2^a} $\end{document}</tex-math></inline-formula> are constructed by symplectic LCD codes.</p>