The space group of LaCrO3 and its variation with temperature was analyzed by selected area electron diffraction (SAED) and by convergent-beam electron diffraction (CBED). All the reflection spots of SAED patterns of LaCrO3 at room temperature could he indexed as orthorhombic symmetry with primitive lattice of a = 5.479. b = 5.516, and c = 7.766 Angstrom. The space group of LaCrO3 at room temperature was determined to be Pbnm (no. 62) from the analysis of CBED patterns. The reflection spots of SAED pattern which indicated orthorhombic symmetry disappeared with increase in temperature up to 300 degreesC. From CBED patterns, it was clarified that the crystal system of LaCrO3 at 300 degreesC was rhombohedral with space group of R (3) over barc (no. 167).