The aim of this paper is to derive and analyze the mathematical properties of a new continuous size-structured model for red coral (Corallium rubrum, L.) growth. Since historical Leslie models 4 are often used to deal with some ecological problems, a new approach is here proposed and give some promising results. The main advantage of using continuous model is that we hope to describe precisely the mass mortality events, observed in Mediterranean sea, and its consequences on red coral dynamics. Simulations' studies allow us to qualitatively discuss some questions about red coral populations dynamics. The development of this method should be useful for the study of the conservation of red coral populations.