In this work, the microstructural defects in SrBi2Ta2O9(SBT) ferroelectric thin films were investigated at the atomic-scale by high-resolution transmission electron microscopy (HRTEM). A stacking fault with an extra inserted Bi-O plane normal to thec-axis was observed in SBT film with 10mol% excess bismuth prepared by metalorganic deposition. Edge dislocations with an average space about 3nm were observed at the small misorientation angle (8.2°) tilt grain boundary of SBT film with (001)-orientation prepared by pulsed laser deposition. The Burgers vectorbfor the edge dislocation was determined to be 1/2[110]α0, where α0is the parameter of SBT unit cell. Chemical compositions of grains and grain boundaries in SBT films annealed in forming gas at 450°C and 500°C for 60 minutes were analyzed by using energy dispersive spectra at the nano-scale. Effects of the microstructural defects and microchemistry of the grain boundaries on the leakage current of SBT films are briefly discussed.