Color information is ignored in most of the image quality assessment m ethods.Color information and luminance information are two important parts in color image.Loss of color info rmation will result in the low consistency of the assessment results.Aiming to the problem,full-quaternion is defined in this paper.It is used to describe the structure information of a col or image.The real part and imagery parts in full quaternion are used to perform the task.It differs from the tradi tional pure quaternion-based color image description method where the detail information in an image is enha nced by using the real part of a quaternion.To enhance the detail information in an image,local variance of lum inance layer and the three color channels are taken as the real part and imagery parts respectively.On the basis of that,the structure similarity (SSIM) measure is studied and the quaternion-based structure similarity measure is use d to perform color image structure comparison.Results from the experiments show that the proposed method combines detail information and color information of a color image.It can describe the structure information better t han the traditional description methods.The quantitative results reveal that the performance of the full quatern ion-based method is better than the pure quaternion-based method and many state-of-the-art methods.The values of Kendall rank correlation coefficient (KRCC),spearman rank correlation coeffici ent (SRCC) and root mean squared error (RMSE) are 0.6929,0.8818and 7.506,respectively,which proves that t he performance of the proposed method is better than the other methods in the experiment.