As a key concept in early mathematics curriculum, number sense is crucial for children's learning of other mathematics concepts. An earlier curriculum with a strong focus on number sense development presumably helps children perform better in mathematics later on. Chinese students outperformed their United States (U.S.) peers on number sense at lower grade levels, and on many other mathematics areas at both lower and higher-grade levels. This study analyzed the representation of number sense and its connection to other mathematics concepts in both traditional and reformed first-grade textbooks in China and the United States, and explored the learning opportunities that the textbooks in each country provide for their children in developing number sense. It found that Chinese textbooks focused more on the meaning and representation of number, place value, base-ten concepts, and on the connection of number sense to number operation while U.S. textbooks focused more on number counting, patterns, and the connection of number sense to data analysis. Thus, the textbooks in the two countries offered different learning opportunities for their students to develop number sense and its connection to other mathematics content. (Contains 6 figures and 5 tables.)