Human-computer interaction is a complex of technical science

which investigates the interaction and communications through mutual understanding between human and computers to solve problems of information managements

services and processing in maximized degree for human needs.This paper proposed a conceptual model of new generation (fourth generation) human-computer interaction systems and their four major features:(1) the ways for interaction are through multimodel perceptions (hearing

vision

gestures and pen writing); (2) the interface for interaction is through the intellegent agents

who may understand user's requirements and implement all required processing by machine through auditory/visual diologues; (3) the contents for interaction may be performed by techniques of content based text or image/video retrieval; (4) the display environment of interaction may be realized in 2-D or 3D through virtual browsing the 3-D scene of computer graphics reconstructed by 3-D computer vision technique.In this paper the possible solutions and algorithms to implement these four major features are given and the platform of the 4th human computer interative system is also described.