Abstract: This paper dealt with the SDS polyacrymide gel electrophoresis of proteins and analysis of the amino acids in the diseased and healthy leaves,at the same side and same height,of the same strain of Paulownia catalpifolia,P. elongata,P. albiphloea and P. kawakamii respectively. The results indicated that the leaves of 4 species of Paulownia tress with witches′ broom had one protein band,of which molecular weight was 12 KD,which did not appear in the healthy leaves free of phytoplasmas. Moreover,the protein quantity in the affected leaves was more than that in the healthy leaves free of phytoplasmas.Moreover,the protein quantity in the affected leaves was more than that in the healthy leaves free of phytoplasmas. At the same time,there was significant difference on the amino acids between the healthy and diseased leaves of P. catalpifolia and P. kawakamii. The amount of cystine in the affected leaves was higher than that in the healthy leaves,but the change of amount of phenylalanine in the affected and healthy leaves was contrary. These changes of proteins and amino acids in the leaves might be related to the witches′broom of the Paulownia trees.