An improvement to quadric-error-metrics-based mesh simplification algorithm is presented in this paper. Firstly， the support region on the original mesh is defined for the new vertex generated in an edge collapse operation

and the connection between the new vertex and the original mesh is established. Secondly，the quadric distance error from the new vertex to its support region is calculated as the global simplification error

and the original quadric error is regarded as the local simplification error; Finally the sum of the two errors is defined as the new cost function of the edge collapse operation. Experimental results demonstrate that the improved algorithm can preserve the details better than the original one and reduce the simplification error obviously.