Range alignment is usually based on the correlation of range profile in ISAR imaging.According to the point scatterer model of target,this paper shows that the range profiles have strong correlation within the aspect change 0.1°,but with the increase of aspect change the correlation will decrease greatly due to cross-term,which also shows that drift error will be caused when conventional neighbor amplitude correlation method is used to align the envelope.It is shown that by averaging over ten range profiles selected from the imaging needed range profiles with equal aspect change,the cross-term can be restrained,and the stable average range profile can be obtained.The average range profile has strong correlation with all range profiles,and if it is used as template,then the accuracy of range alignment can be enhanced.An iterative correlation alignment method for range alignment is proposed by using global optimization criterion.Real data validate its effectiveness.