In order to understand the effects of SO₂ stress on chlorophyll biosynthesis of two goldenleaf shrubs (Ligustrum × vicaryi and Ligustrum japonicum  Howardii’) and investigate possible acting sites of SO₂ stress on chlorophyll biosynthesis, the activities of key enzymes involved in chlorophyll biosynthesis, the contents of chlorophyll and its intermediates were analyzed under different SO₂ treatments through an artificial static fumigation system. The results showed that the contents of Urogen Ⅲ, Proto Ⅸ, Mgproto Ⅸ, and chlorophyll a and b were increased with the rising of SO₂ concentration, then decreased at SO₂ concentration of 80 mg·m^-3. Furthermore, the activities of ALAD and UROS exhibited a similar trend. In contrast, the contents of ALA and PBG in the control were significantly lower than under the 20 and 40 mg·m^-3 treatments, and greatly higher than under 80 mg·m^-3. The results also indicated that changes of these factors related to chlorophyll biosynthesis were greater in Ligustrum × vicaryi than in Ligustrum japonicum ‘Howardii’, which implied that the latter was more resistant to SO₂ stress than the former. All the results predicated that chlorophyll biosynthesis in leaves of two goldleaf species was presumably blocked at the step from PBG to Urogen Ⅲ under the SO₂ stress.