During the Chinese Revolution in 1949, three couples flee from China to the island of Taiwan. Gen. Lei Yifang (Huang Xiaoming) returns to Shanghai highly decorated, and swiftly wins the hand of wealthy debutante Yunfen (Song Hye-kyo). Yen Zekun (Takeshi Kaneshiro), a Taiwanese doctor settling down to normal life in his hometown after years as a forcibly drafted field medic in the Japanese army during WWII. Perhaps a little more than conveniently, he meets Zhou, who has moved into the house once occupied by his Japanese paramour Masako (Masami Nagasawa) – a friendship anchored by their shared longing for a distant beloved. Yu Zhen (Zhang Ziyi), an illiterate young woman who came into the equation when Tong pays her to have a photograph taken together as a couple as a proof of marriage, which would provide his family back home with more food rations. This financial exchange is a harbinger of Yu’s unraveling existence, as unforgiving circumstances eventually force her to go into prostitution so as to secure enough money to travel to Taiwan with hope of finding her missing lover.
電影講述在1945年中國抗日战场，中國軍隊將軍雷義方（黃曉明 飾）在平原戰場上率兵大敗日軍，軍隊的通訊兵佟大慶（佟大為 飾）俘獲了台灣籍日軍軍醫嚴澤坤（金城武 飾）。日軍投降後，三人各自其生活。雷義方返回上海，在舞會上認識了富豪千金周蘊芬（宋慧喬 飾），兩人一見鐘情，並很快結婚了。但好景不常，內戰爆發了，同時，他的夫人懷孕了。 嚴澤坤在抗戰後回到台灣，卻發現曾經的戀人日本女孩志村雅子（長澤雅美 飾）已經被遣返回日本。但由於嚴的母親不喜歡二人來往，她把雅子寄來的信全都燒毀，以致二人失去聯繫。未婚的佟大慶於再次召集時，為了家人得到更多的糧食配給，他請白天做護士照顧傷兵的于真（章子怡飾）拍張照片證明已婚，沒想到真的成了一對苦戀的情侶。國共大戰中，國民黨的軍隊全面潰敗。雷義方在战死前托佟大庆一定要把自己的日記本交給妻子。 在內戰快要結束之際，嚴澤坤的弟弟嚴澤明（楊祐寧 飾）因见到大哥严泽汉被诬陷为共产党被枪毙，对时局极端失望，去大陸参加了学生运动。严泽坤為了維持在苦難中風雨飄搖的家庭，他代替去世的大哥而娶了嫂 嫂，表面上為購買藥品实为找回弟弟而登上往返基隆与上海间的郵輪“太平輪”。表面上的他風平浪靜，內心卻一直沒有停止思念因戰爭被迫分離的日籍戀人雅子。 當時的中國，人人千方百計都想登上太平輪，離開上海到台灣。這艘船彷彿成為人們最後的希望。沒想到，意外的沉船改變了所有人的命運，船上近千人絕大多數都 在海難中遇難。 眾人相逢在開往台灣最後一班的“太平輪”上，究竟這三對戀人刻骨銘心的愛情故事，彼此間的微妙關係，命運的齒輪互相緊扣，大時代下各人該何去何從呢？