Based on the cut and projection description of quasicrystals, a method for calculating section projection diagrams of quasicrystals is developed and applied to decagonal quasicrystals. Firstly, a section projection diagram parallel to the quasiperiodic plane of perfect decagonal quasicrystal is calculated. By using the existing elastic displacement field formulae, section projection diagrams parallel to the quasiperiodic plane of a decagonal quasicrystal containing a straight dislocation along periodic direction have been calculated when the phason strain and the phason phonon strain are introduced respectively.