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Wheat is a major staple food and its sensitivity to the gas pollutant ozone (O 3 ) depends on the cultivar. However, few chamber-less studies assessed current ambient O 3 effects on a large number of wheat cultivars. In this study, we used ethylenediurea (EDU), an O 3 protectant whose protection mechanisms are still unclear, to test photosynthetic pigments, gas exchange, antioxidants, and yield of 15 cultivars exposed to 17.4 ppm h AOT40 (accumulated O 3 over an hourly concentration threshold of 40 ppb) over the growing season at Beijing suburb, China. EDU significantly increased light-saturated photosynthesis rate (A sat ), photosynthetic pigments (i.e., chlorophyll and carotenoid), and total antioxidant capacity, while reduced malondialdehyde and reduced ascorbate contents. In comparison with EDU-treated plants (control), plants treated with water (no protection from ambient O 3 ) significantly decreased yield, weight of 1000 grains, and harvest index by 20.3%, 15.1%, and 14.2%, respectively, across all cultivars. There was a significant interaction between EDU and cultivars in all tested variables with exception of A sat , chlorophyll, and carotenoid. The cultivar-specific sensitivity to O 3 was ranked from highly sensitive (> 25% change) to less sensitive (< 10% change) by comparing the difference of the average grain yield of plants applied with and without EDU. Neither stomatal conductance nor antioxidant capacity contributed to the different response of the cultivars to EDU, suggesting that another mechanism contributes to the large variation in response to O 3 among cultivars. Generally, the results indicate that present O 3 concentration is threatening wheat production in Northern China, highlighting the urgent need for policy-making actions to protect this critical staple food.