We propose a method for the analysis of the stress-strain state of rectangular orthotropic plates under the conditions of biaxial tension and shear. According to this method, we specify a field of displacements in the plate in the form of the product of a matrix of differential operators by an unknown vector function or a column of three scalar functions, each of which admits a representation in the form of the sum of the products of an unknown function of one variable by a trigonometric function of the other variable. The number of independent coefficients of each function is determined from the boundary conditions by the method of Fourier series. We also performed calculations of the stressed state in the plate depending on the ratio of its sides and the type of loading.