The study measures syntactic complexity and register features of the English version of the free trade agreements signed by China and the United States with other countries, and analyzes similarities and differences between the two types of stylistic features. Research shows that the free trade agreements signed by China pay more attention to the rigorous choice of words and terminology. The agreements have generally low syntactic complexity and high readability and adjust to the English way of expression. The syntactic complexity of the free trade agreements signed by the United States are higher, with more clauses used. Their style is influenced by the ruling party and leaders, and the syntactic complexity shows diachronic changes. This study provides references for teaching and research of business stylistics.