孙悟空（郭富城饰）、猪八戒（小沈阳饰）和沙僧（罗仲谦饰）一路打打闹闹保护师傅唐僧（冯绍峰饰）去西天取经，不料偶然闯进了神秘的西梁女国——一个从未有过男人的国家。女儿国国王（赵丽颖饰）对唐僧一见钟情，却因不知情为何物自以为患上是绝症的「相思病」，国师（梁咏琪饰）警告国王男人乃剧毒生物，并下令处死唐僧一行人。师徒四人在国王的协助下逃离法场，但唐僧、八戒和沙僧却在打斗中误饮子母河水而意外怀孕。就在孙悟空施展72变解救师徒三人时，唐僧似也打烂斋砵对国王渐生情愫…..师徒四人的闯进也引来了河神（林志玲饰）现身，彻底打破了女儿国的平静。河神的怒意淹没了整个女儿国，西梁女国陷入了灭国危机！究竟在爱一个人和爱众生之间，唐僧会如何抉择？孙悟空如何力敌河神同时解救陷入情关劫难的师傅师弟？国师国王面对灭国危难如何挽救国民？

On the conflict-packed journey to the West, Wukong (Aaron Kwok), Bajie (Xiao Shenyang), Sha (Him Law), and Xuanzang (Feng Shaofeng) accidentally enter the Womanland of Western Liang, a mysterious country where no men have ever existed. The Queen (Zhao Liying) falls for Xuanzang at first sight, without knowing what love is, thinking she could be ill with the incurable lovesickness. The Preceptor (Gigi Leung) warns her that men are all poisonous creatures and orders to kill Xuanzang and his disciples. The Queen helped the four to flee, however, Xuanzang, Bajie and Sha drank the water from the Motherhood River without knowing that will cause them to be pregnant. Wukong tries to save the three, meanwhile Xuanzang gradually loses his stand and starts falling in love with the Queen. The trespass of the four men agitated the God of River Oblivion (Lin Chi-Ling), who breaks the peace of the Womanland; the whole nation is flooded in a fury and puts it at risk of total destruction. Will Xuanzang choose to love an individual or all the other sentient beings? How will Wukong fight to subdue the River God and rescue his master and brothers out of their trouble of love? How will the Queen and the Preceptor save their people from this crisis?