Abstract: In this paper the effect of colouring temperature, colouring time and particularly heat treatment on the colouring of plate glass by silver diffusion has been reported. XPS,AES and EDAX were used to study the composition of the coloured layer and the state of colouring material in plate glass. The results showed that the effective eomponent in colouring agent is AgO before heat treatment, which then changes into metallic silver after heat treatment. The shade of coloured glass got deepened probably due to the particle growth of the colloidal silver after heat treatment.