Direct digital frequency synthesizer (DSS) was proposed by Tiemey at 1971 and this frequency synthesis technique soon came to the attention of people because of its good frequency resolution and fast frequency performance. Now, it is extensively used in telecommunication and electronic machine region and it is a key technology to realize full digitalization. This text introduces the principle and characteristics of DSS and gives the method of implementing DDS using VHDL. The design proposal touches on MAX+PLUS II platform. By this way, we can make the Chip products instead of multiple chip board products, so as to reduce power consumption, improve reliability, and also can be easily to design on line modification.