<p style='text-indent:20px;'>We study a family of non-simple Lie conformal algebras <inline-formula><tex-math id="M2">$ \mathcal{W}(a,b,r) $</tex-math></inline-formula> (<inline-formula><tex-math id="M3">$ a,b,r\in {\mathbb{C}} $</tex-math></inline-formula>) of rank three with free <inline-formula><tex-math id="M4">$ {\mathbb{C}}[{\partial}] $</tex-math></inline-formula>-basis <inline-formula><tex-math id="M5">$ \{L, W,Y\} $</tex-math></inline-formula> and relations <inline-formula><tex-math id="M6">$ [L_{\lambda} L] = ({\partial}+2{\lambda})L,\ [L_{\lambda} W] = ({\partial}+ a{\lambda} +b)W,\ [L_{\lambda} Y] = ({\partial}+{\lambda})Y,\ [Y_{\lambda} W] = rW $</tex-math></inline-formula> and <inline-formula><tex-math id="M7">$ [Y_{\lambda} Y] = [W_{\lambda} W] = 0 $</tex-math></inline-formula>. In this paper, we investigate the irreducibility of all free nontrivial <inline-formula><tex-math id="M8">$ \mathcal{W}(a,b,r) $</tex-math></inline-formula>-modules of rank one over <inline-formula><tex-math id="M9">$ {\mathbb{C}}[{\partial}] $</tex-math></inline-formula> and classify all finite irreducible conformal modules over <inline-formula><tex-math id="M10">$ \mathcal{W}(a,b,r) $</tex-math></inline-formula>.</p>