Employing data of a Meiyu front rainstorm during 5-6 July,1991,in the Changjiang -Huaihe Basins with the aid of surface precipitation distribution,the diagnosti c characteristics of wet Q-vector (QV),quasi-,semi-and ageostrophic-QV are exami ned qualitatively on a vector field(VF)basis.The results show:as far as the dia gnostic features of wet QV,quasi-,semi-and ageostrophic-QV are concerned,the thi rd is superior to the second one, that is worst of all,and the first is almost t he sa me as the last.Furthermore,they are advantageous over the second and the third o bviously;the vector convergence field (VCF)at 700hPa of each QV is better than t hat of itself at 850hPa and 500hPa in reflecting precipitation,especially,the VC F at 700hPa of ageostrophic-and wet-QV have good indications to synchronous rain fall;the QV VCF corresponding to precipitation lies basically in front of a trou gh and in the middle or rear of a cyclone,which can act as a reference tool to o perational job.