Abstract: Pectate and pectin lyases are a class of polysaccharide lyases produced by a diverse group of organisms including bacteria,fungi,plant and nematodes.Various pectate lyases and pectin lyases are divided into five families.By NCBI BLASTX server,tomato P56 amino-acid sequence was compared with other pectate and pectin lyases belonging to polysaccharide lyase family Ⅰ28 proteins,with higher identity of amino acid sequence compared to P56 amino-acid sequence,were obtained.On the base of the constructing phylogenetic tree using PAUP 4.0,MP(phylogenetic trees) and NJ(neighbor-joining) trees of diverse pectate and pectin lyases showed that pectate lyases from plant,pectin lyases from fungi and pectate lyases from bateria belong to different groups,respectively.The pectate lyase A of Aspergillus nidulans is more closely related to plant pectate lyases than to pectin lyase from fungi and pectate lyases from bacteria.The pectin lyase from Pseudomonas syringae is more closely related to fungi pectin lyases than other lyases.