By simultaneously analyzing chlorophyll a fluorescence transient and light absorbance at 820 nm, gas exchange and activities of key scavenging enzymes of reactive oxygen species (ROS) in chloroplasts, we investigated the effects of Pb treatments with different concentration on photochemical activities of photosystem I (PSI) and photosystem II (PSII) and on photosynthesis in maize seedling leaves, and analyzed the interaction of PSI and PSII. The results showed that Pb treatments restrained growth significantly, decreased pigment content. The Pb treatments decreased net photosynthetic rate via non-stomatal limitations in the maize leaves, which increased the excess excitation energy. The Pb treatment also inhibited the activities of SOD and APX and damaged the reaction centers, donor and acceptor sides of PSII and the photochemical activity of PSI in maize leaves.