He is famous as the author of the Jigu Suanjing (Continuation of Ancient Mathematics) one of the Ten Computational Canons.
In 623, together with Zu Xiaosun, a Civil Servant, he was assigned to report on problems with the calendar—although only recently adopted, it was already out of step with the eclipses.
In fact, Wang did not approach this in a sophisticated way; he proposed to ignore the irregularity of the sun's motion and also the precession of the equinoxes—both had already been incorporated in calendar calculations by Zu Chongzhi in the fifth century.
His major contribution was the Jigu suanjing ("Continuation of Ancient Mathematics" 缉古算经), written before year 626.
The book contains 20 problems based mostly on engineering construction of astronomic observation tower, dike, excavation of a canal bed etc.