To solve the generation and update of background model in moving target detection,firstly,an approach to background generation based on modified K-means clustering algorithm was proposed in this paper.The concept of Dynamic Three-dimension Group (DTDG) was given and each pixel was modeled using three DTDGs.The approach got background extraction.Secondly,a novel approach of adaptive background model was presented.Any pixel was modeled by one new DTDG.Updating decisions were made according to the pixel dynamic change information.The approach can update the background to adapt slowness,sudden changes in illumination and moving background targets automatically.The experimental results demonstrate the effectiveness of the proposed approach.