The invention discloses a converter alkalinity dynamic control method which is characterized in that single-slag operation is carried out on the basis that the content of silicon [Si] in molten iron is greater than or equal to 0.15 wt% and smaller than or equal to 0.8 wt%, parameters such as final temperature, endpoint carbon content, end phosphorus content, dephosphorization efficiency and convertor slag quantity can be set and adjusted to correct the alkalinity, so as to realize dynamic linear adjustment on the alkalinity. According to the converter alkalinity dynamic control method, the requirements on the slag quantity, slag alkalinity and end phosphorus content, as well as the influences of various factors such as the final temperature and the endpoint carbon content on the dephosphorization effect are comprehensively considered, the dynamic linear adjustment on the alkalinity is realized, dephosphorization is realized at the lowest cost, and a popularization and application value in a steelmaking manufacturing plant is achieved.