Dynamic changes of leaf growth and three physiological indexes of Platanus × acerifolia ( Ait.) Willd. Were studied in leaf expansion stage. The results show that in leaf expansion stage (April 4 to April 26), the weight and area of individual leaf increase gradually, and reach their peaks on April 26 and rise to 9. 8 and 39. 2 times of that in the initial stage, respectively. With the growth of P. × acerifolia leaf, the chlorophyll content has an increasing trend, and the increasing range is great. Protein content and POD activity appear a declining trend, and the declining range is great. All the three physiological indexes have some minor fluctuations. Contents of Chla, Chlb and Chl ( a + b) are the highest on April 26 and rise to 3. 41, 5. 91 and 4. 00 times of that in the initial stage. Protein content and POD activity reach the lowest points on April 26 and April 16, respectively and decline by 73. 42% and 94. 41% of the initial stage of leaf expansion.