Abstract: In order to study the photosynthetic characteristics of evergreen plants in northern winter haze, net photosynthetic rate（Pn）, stomatal conductance（Gs）and intercellular carbon dioxide concentration（Ci）of the plants were measured with 4 evergreen plants in Tianjin,including Euonymus japonicus, Populus simonii, sisal and prive by CL-340 portable photosynthesis instruments. The effects of haze was analyzed on the photosynthetic characteristics of four evergreen plants , the differences and the relationship among four plants. The results show that Pn was the highest in Populus simonii and was the lowest in Euonymus japonicus in three sunny days. Gs was lowest in Euonymus japonicus and sisal, but was highest in Populus simonii and Privet. Ci was the highest in Euonymus japonicas and was the lowest in Privet. The difference of Pn in each species was positively correlated with the change of Gs, the correlation coefficient was 0.923. Pn, Gs, and Ci of the four plants were significantly decreased in haze days. Sisal has higher Pn, lowest Gs and the highest Ci under heavy haze. This conclusion was different from the sunny conditions. It means that the haze reduced Pn of Populus simonii and Privet largely, the Ci of Euonymus japonicus and increased Ci of Privet at the same time. In the case of heavy haze, the difference of net photosynthetic rate（Pn）among the four plants was not correlated with the change of stomatal conductance（Gs）, the correlation coefficient was 0.096,which is completely different from that of sunny days. From 11 to 17 in January 2017 with haze, Gs of four plants were significantly highly correlated with Pn. The correlation coefficient was above 0.8.

Key words: winter, haze, evergreen plants, photosynthetic characteristics