Abstract: A semi-analytical model and the corresponding precise method for laminated composite beams are presented. Firstly, dividing the in-plane area evenly and then gives the semi-analytical equations for every layer by using the modified Hellinger-Reissner variational principle. Then divides each layer evenly into several sub-layers, and transforms the semi-analytical equations to a set of algebraic equations which have almost no discrete errors with the precise integration relationship between the adjacent sub-layers. Finally, establishes an efficient reduction method by using the block tridiagonal matrices form of every algebraic equation of layers. The present method not only has high accuracy and efficiency, but also can deal with various boundary conditions including delamination conditions. Furthermore the method overcomes the influence of ill-conditioned matrices. Numerical examples show the validity of the present method efficiently.