Abstract: 【OBJECTIVE】 Comparatively peroxidase (POD) and isoenzyme of roots, stems and leaves in tobacco infected with Pseudomonas solanacearum were studied in order to offer academic foundations for breeding resistive plants. 【METHOD】 Colorimetry for POD activity and polypropylene amic gel electrophoresis (PAGE) for isoenzyme were used. 【RESULTS】 After inoculated by Pseudomonas Solanacearum, it was found that there was higher peroxidase (POD) activity in leaves than that in roots and in stems, and the POD activity in roots, stems and leaves was highest in 3 days but in leaves which improved 29.67% percent than those form the contrast. Isoenzyme electrophoresis showed that difference occurred in numbers and types of isoenzyme bands and related activity of every band between different samples. 【CONCLUSION】 POD was a protectal enzyme and it was changing with infection, so it was suggested that POD may have close relation to resistance against disease.