Abstract: VHDL-AMS is an extension of VHDL to analog and mixed-signal domain.VHDLAMS provides designers the ability to deal with complex system design at conceptual level.With the standardization of VHDL-AMS,capable and effective simulators are in demand for exercising complex analog and mixed-signal models.In the article the main concept of VHDL-AMS in analog extension is introduced.A mixed-mode simulation environment is presented.The main steps of the analog solver are described.The synchronization of continuous and discrete-event simulation are discussed.Four examples indicate how VHDL-AMS is used in conceptual design.