西门庆（林伟建 饰）是个长相俊美，家境殷实的公子哥。少年时期就跟随父亲（徐少强 饰）修习房中术，得父亲真传精通男女情爱之事。就在其学有所成之际，其父更是聘来了一名长相媚惑的女子紫烟（上原カエラ Kaera Uehara 饰）来让西门庆实践自己所学的房中术。就这样，在父亲的指导下，西门庆渐渐成了一个沉迷风月不问情事的男子。一次出门游历结识了尼姑明月（若菜光 Hikaru Wakana 饰），一夜云雨令明月春心大动，遂还俗与他结发为妻。西门庆不仅熟于男女之事，更是对人情世故得心应手。善于钻营，巴结权贵，贵族名人知县知府都和他往来。父亲死后，继承了满贯家财的西门庆生活的更是风生水起，过的纵欲放荡不受世俗牵绊。偶然的机会，他看上了长相俏丽的小媳妇潘金莲（早川濑里奈 Serina Hayakawa 饰），然而偷情的生活已然不能让他满足，于是他打起了毒害其夫武大郎的主意…
　　该片改编自长篇世情小说《金瓶梅》。


此次钱文琦拍摄的《金瓶梅》被定为三级，也既是“未成年观众不能入场观看”。由于一开始就直指情色，找来日本三位AV女优上原kaera、若菜光、早川濑里奈过来主演，因此在尺度上并无遮遮掩掩，被香港电检定为三级是预料之中的事。
钱文琦之前是王晶的副导演，曾拍摄过《玉女心经》、《蜜桃成熟时2、3》、《南洋十大邪术》等电影。由于近年香港情色影片低迷，脱星纷纷上岸，能有市场的新人已经是屈指可数。于是，众多香港制片纷纷把眼光瞄准临海的日本。日本AV繁荣，女优辈出，大胆程度和价钱都能让香港制片满意，像早前古天乐、陈奕迅主演的《豪情》、彭浩翔导演的《AV》裸露场面请的都是日本AV女优演出。
钱文琦开拍《金瓶梅》也同样走上这一途径，请了日本上原kaera、若菜光、早川濑里奈AV女优参演。有这些不惧“牺牲”的女优，《金瓶梅》的激情程度也就可想而知了。
《金瓶梅》海报其中一句广告语是：“大开色戒”，这当然是因李安的《色戒》火爆而起，但以这部电影走的路子，比《色戒》镜头大胆暴露是不在话下的事。在此片扮演小尼姑的若菜光就牺牲颇大，把一头秀发给剃掉——演三级片露三点见多不怪，但需要连头发都剃掉，完全“裸体”就真是少到仅有了。

　　This long-lost masterpiece of hardcore gay erotic cinema centers on a handsome young stud who rides his motorcycle through myriad sexual encounters, from a soccer game’s locker room to a phantasmagoric and deeply melancholy orgy. A labyrinth of all-male fantasies whose outstanding beauties always end up fading away while leaving their sensual protagonist dealing with his own loneliness, EQUATION was directed with supreme grace by the mysterious Dietrich de Velsa (aka Francis Savel/Frantz Salieri). A former painter, de Velsa was also the owner and artistic director of La Grande Eugène, one of the first drag cabarets in Paris. Years later, he collaborated with Joseph Losey on MR. KLEIN (1976) and DON GIOVANNI (1979). His one and only film, EQUATION TO AN UNKNOWN stands as one of the most extraordinary erotic films of all time.
　　“The most melancholic porn film I’ve ever seen. It’s very sad, and aesthetically beautiful. Just a young man wandering through several depictions of love and choreographies of love-making it’s like a ceremony, a ceremony of fantasies, especially the last sequence where the main character recalls all his previous fantasies, which come one by one around his bed and make love to him. I think it’s one of the most beautiful film sequences of French cinema.” –Yann Gonzalez