Six representative winter wheat cultivars were planted at five locations with the latitude varied from 32 degrees N to 36 degrees N in Henan Province to study the effects of latitude on their grain's protein components. The results showed that with increasing latitude, the contents of albumin and gliadin decreased, while glutenin content, glutenin/gliadin ratio, sum of protein components, and grain yield increased. The grain's albumin content of test cultivars at Xinyang, gliadin content at Zhumadian and Xuchang, and glutenin content and glutenin/gliadin ratio at Wuzhi and Tangyin were higher than those at other locations. The average air temperature, total sunlight hours, and precipitation in May had close relations with the grain' s protein components of test winter wheat cultivars at different locations. In order to improve wheat grain quality, suitable cultivars should be chosen to match the local ecological conditions, and, management practices for improving photosynthesis and extending grain-filling period should be performed in May.