Data has become one of the essential driving forces for value production in the digital era, and accelerating the cultivation of the data-factor market has become an important strategy for the growth of China’s digital economy. Meanwhile, data is a competitive advantage for firms. The paper explores a scenario where a single data supplier exists in the data market, with two competing firms on the demand side.Competing firms can obtain the same data from the data supplier, and put it into production to provide consumers with personalized products. The paper investigates data purchase strategies of demand-side firms and finds that, for competing demand-side firms, data-driven product personalization intensifies price competition in the product market, reduces firm profits, and increases consumer welfare. The optimal strategy for the data supplier is to sell to both competing firms when offering a uniform price and selling to only one firm when he provides differentiated prices to maximize his profit. Our findings have implications for the formulation of the data market’s trading rules, participation strategies of the demand side, and data pricing strategies for the supply side.