Set in World War II, Casino Tycoon chronicles the story of Benny (Andy Lau), a young graduate played by Andy Lau, who flees Hong-Kong during the Japanese invasion and heads for gambling haven Macau. Once in Macau, he starts as a lowly coolie but he impresses a local business man who has ties to organized crime, and slowly builds his way up the ranks. Benny engages in a battle of wits against his college rival and business enemies. In the finale, Benny overcomes his enemies but at great personal cost.
賀新童年時家中富有，但十二歲那年的大年初三，因父親及伯父投資洋行失利破產而家道中落，大伯更因此吞槍自殺，遺下自己和母親相依為命。
某日賀新到母親表哥的牙醫診所接受治療，卻因為付不起診金而在未施打麻藥的情況下被強拔兩顆門牙，劇痛與羞辱難當的賀新悲憤地向母親發誓將來要發達有錢，不再因窮被人看扁。
長大後，賀新成為了成績優異的物理系大學生，更與家境優渥的大學同學程樂兒交往，但大亨傅老揸之子傅家俊也喜歡程樂兒，所以傅家俊極度厭惡賀新，處處為難他，也看不起賀新出身低微，兩人從大學時代起就勢同水火。
一九四一年平安夜香港淪陷，賀新被迫中断学业并與好兄弟郭英南逃到澳門避难，兩人在码头做苦力时，获得运输公司老板阿芳素（他也是贺新在香港读书时的老师白神父的好友）的看中，但亦与傅老揸手下的賊人王昌产生矛盾。賀新和郭英南於賭場見識時，與擔任賭場總管的聶傲天惺惺相惜，更獲引薦為賭場老闆傅老揸效力，贺新出主意更换了骰子底盘的材质，令近期一直在赌场靠听骰子分辨点数赢了很多钱的三位赌徒输光钱财。
