This paper presents a multiscale method to estimate the elastic property of the 13_3 microtubule. A microtubule is viewed as being formed by rolling up its planar encounter into the tubular shape, and the transformation is written into a set of equations with three geometrical parameters. The representative cell is chosen as an unit of two pairs of tubulin momoners. With the appropriate longitudinal and lateral interactive potentials, the strain energy density is calculated by deviding the cell’s energy by its spacial volume. The elastic property of microtubule is determined by minimizing the strain energy density, and the elastic constants are calculated in the thereotical scheme of orthotropic elasticity due to the geometrical meanings of the induced parameters. The advantage of the proposed method and its future application are discussed.