The SAGA Synchrotron Light Source is a compact third generation synchrotron light source with a 1.4GeV electron storage ring, and being constructed in Tosu City, Saga prefecture Japan. A distributed dispersion system, the dispersion function is non-zero in long straight section, is adopted for the lattice design to make the ring to be compact. At the typical working point (5.796, 1.825) the emittance without insertions is 25nm-rad and the beam size at the middle of the long straight section is about 0.58 mm in horizontal and 0.13mm in vertical (10% coupling is assumed). One of merits of distributed dispersion system is reduction of sextupole strength required for chromaticity correction. Consequently, a large dynamic aperture can be obtained. We have performed beam dynamics studies by using TRACY2 to estimate tolerable magnetic errors and magnetic misalignments and found that the designed lattice has an enough dynamical aperture to operate the ring.