Wang Zhengfang was born in 1938 and spent his childhood in Beijing. His father, linguist Wang Shoukang, was a professor in the Department of Chinese Literature of Beijing Normal University at that time, and he was also the vice president of the "Mandarin Tabloid" founded by the Ministry of Education. In 1948, the Nationalist government decided to establish the "Mandarin Daily" in Taipei, and hired Wang Shoukang as the vice president. Therefore, in the spring of 1948, Wang Zhengfang moved to Taiwan with his family. He was admitted to study National Taiwan University's Department of Electrical Engineering. At that time, there was a prejudice in Taiwanese society that "good boys should not study liberal arts". He went to continue his studies in the United States, and was at one time blacklisted from both sides of the Taiwan strait at the same time. In the 1980s, Wang Zhengfang, who was over his age, felt that there was a "calling voice" in his heart, evoking his hidden drama ability and talent. After all, being an engineer, the professor's life is comfortable and stable, and drama and film are unknown to him. However, after thinking about it for a while, he resigned from the university teaching position and plunged into the film circle.

王正方祖籍河北武邑，抗日战争中在家人逃难地长沙出生，抗战胜利后迁回北平。1948年父亲王寿康出任台湾《国语日报》副社长，全家赴台。在台先后就读国语实小、建国高级中学和国立台湾大学电机系，后留学美国宾夕凡尼亚大学，获电机工程学博士。毕业后在美曾任IBM工程师、乔治梅森大学工程系副教授等职。

保钓运动兴起时，王正方在美国积极参与，并于1971年11月成为秘密访问中国大陆晋见周恩来的五位保钓代表之一。事后被中华民国政府列入黑名单，曾长期无法回台。

1982年，辞去教职投入电影业，曾任演员、编剧、导演。编剧兼主演的香港电影《半边人》曾获第3届香港电影金像奖最佳电影，并入围最佳男主角和最佳编剧。

近年积极写作回忆性文章，出版文集数册和回忆录。

其兄为药理学家、中央研究院院士王正中。