1，only by doing 常和将来时will 或情态动词连用。

中文意思是“只有通过做某事”。例如，只有通过努力工作你才能享受美好生活和拥有更好的未来。Only by working hard can you enjoy a better life and have a better future.只要通过努力学习，你将在学习中取得更大进步。Only by studying hard will you make greater progress in your studies.2，only by then 常和过去完成时连用，中文意思是“只有到那个时候”例如，只有到那时，他才意识到知识对工作的重要。Only by then hadhe realized the importance of knowledge to his work.