Abstract: With the wide application of multivariate statistical process control techniques,extensive attentions have been paid to the quantitative calculation of multiv ariate process capability indices.It has been relatively difficult to calculate the multivariate process capability indices,considering the complexity of multivariate processes.None of the existing calculation methods is of universal applicability.This paper firstly reviews and analyses recent literatures on multivariate process capability indices.Secondly,it focuses on Taamalgorithm of multivariate process capability index based on the ratio of volume,profoundly discusses its main disadvant ages and puts forward an improved algorithm.Finally,it comparatively analyzes the improvement effect of the new algo rithm of process capabilit y index by making use of the classic case from Jackson's bivariate process.The calculation results show that Taamalgorithm hasinternal defects and our improved algorithm is more reliable.

Key words: process capability, multivariate normal distribution, multivariate process capability index