The cDNA of crayfish (Procambarus clarkii) infected with white spot syn drome virus(WSSV) were used as tester and that of the control as driver to construct a forward subtraction.A reverse subtraction was performed by used tester as driver and driver as tester at the same time.The subtracted products were cloned into the PinPoint^TM Xa-1 T-Vector.Then the recombinated plasmid was transformated into DH5α.A forward subtracted cDNA library including 1620 clone and a reverse subtracted cDNA library including 400 clone were constructed respectively. Using sequences flanking the cloning site as primers,1514 clones were amplified from the 2020 clones constructed by suppression subtractive hybridization.1221 clones of these were got from forward subtraction library and 293 clones from reverse subtraction library. After concentration and degeneration the PCR fragments were robotically printed onto nylon membrane to make a cDNA chip. In the end, 255 positive clones from forward subtraction library and 23 positive clones from reverse subtraction library were detected by cDNA chip.