The cultivation of redclaw crayfish (Cherax quadricarinatus) is developing in recent years. The disease of Cherax quadricarinatus was one of the major factors in its culture and even caused redclaw crayfish to die. The viral disease was found in polyculture of redclaw crayfish with Penaeus vannamei. Haemolymph and homogenated gills from diseased Cherax quadricarinatus was filtered and injected to the healthy Cherax quadricarinatus and all injected animals died within 3-5 days, while animals injected with other tissues including hepatopancrease and stomach were still alive. Examination by electron microscopy showed that there were a number of bacilliform viral particles in the nuclei of haemolymph and gill tissues. The virions varied in (225.6-280.5) nm×(73.2-176.8) nm. The detection of the gills and haemolymph by nucleic acid probe and PCR proved that the virus from Cherax quadricarinatus was similar to WSSV. The BLAST results of the sequence showed that it has 100% homology with respect to sequence of AF332093. The sequence reported in this paper has been deposited in the GenBank database (accession number EF078890). The results indicated that this virus belongs to WSSV Chinese. The C.quadricarinatus bacilliform virus could be detected by WSSV nucleic acid probe and PCR. Key words：Cherax quadricarinatus; bacilliform virus; viral diagnosis