"長江七號"劇情描述一位窮困潦倒的父親（周星馳飾）帶著兒子小迪(徐嬌飾)住在一棟破屋裏，一家全靠老爸做苦力維生，還常常到處撿破爛當家用。但望子成龍的爸爸，還是咬緊牙關讓小迪讀明星學校，並不惜賣命掙錢支付高額的學費；而小迪也因家境清寒之故，經常成為師生取笑欺負的對象，惟獨美麗善良的袁老師〈張雨綺〉對他始終關愛有加，不離不 棄。
看著同學開心的玩著新科技玩具狗"長江一號"，眼紅的小迪成天也吵著父親想買一隻來陪 伴。禁不住兒子的要求，口袋空空的老爸只好把從垃圾堆裏撿到的塑膠球帶回家當禮物。沒 想到，這顆球不但變身成一隻可愛的外星生物，還身懷眾人意想不到的超能力！
欣喜若狂的小迪將這個新朋友命名為"長江七號"，並偷偷瞞著父親和同學將它帶到學校作 伴，期望小巧玲瓏但看似能力非凡的長江七號能幫他教訓欺人太甚的同學，以及解決學校裡 所有疑難雜症。父子兩人悲苦的命運真的會因為外星生物長江七號的降臨而改變嗎？
2008年1月31日(四)起全亞洲陸續上映
As with the title CJ7, the earlier working titles, Yangtze River VII and Long River 7, referred to the Chinese manned space program. The mission of Shenzhou 6 was completed in 2006 and the real Shenzhou 7 is set to launch in September 2008.
The film will have a budget of $20 million US, and will be heavy on CG effects.
Chow plays a man who lives in a partly demolished house. He takes in a homeless boy (who is actually played by a girl, Xu Jiao). Whether the semi-demolished house and the homeless boy are on Earth, or on the alien planet is not clear. As Chow's character can't afford to buy a toy for the child, he finds a makeshift toy in the garbage and brings it back to his "son". The "toy" is actually a powerful alien device and the aliens are desperate to get it back.[4] Some rumours state that it is a "pet" rather than a "toy".
The reason Chow's character can't afford to buy the child a toy is because he is fired without pay from his part-time job as a construction worker. His boss is a contractor played by Lam Chi Chung.
Chow plays an astronaut who crashes his spacecraft on another planet. He befriends an android translator (played by Kitty Zhang) who can communicate with aliens.
Scenes include Chow's character being taken to hospital after seemingly plunging to his death; the adopted child crying, whilst Kitty Zhang's android character plays teacher; a birthday party for the child.
