Fine arts, in recent years, with the rapid development of information technology, its diverse artistic expression trends to be more obvious, at the same time, the artistic expression based on multimedia has been paid more attention by the fields. This paper firstly analyzes the general characteristics of art image fusion process in multimedia environment. On this basis, the digital-to-analog conversion (DAC) method of multimedia artistic expression is proposed, which takes the Gauss Pyramid as basis. In order to verify the scientificity of this method, this paper adopts the empirical method to carry on the empirical analysis. The results show that multimedia artistic expression behavior of fine arts based on this method is significant, and has strong practicability and operability.