In order to understand the distribution of the SpHtp1 gene among different saprolegnia strains,using Saprolegnia parasitica (ATCC200013TM) genomic DNA as the template,a pair of gene-specific primers was designed,a PCR method was developed and the parameters for PCR amplification was optimized.The PCR product was extracted,linked into pMD18-T vector and then cloned into E.coli DH5α.The recombination plasmid was identified by PCR and sequenced to prove the amplification of the target gene.As a result,a 224 bp DNA fragment of the SpHtp1 gene can be amplified from the saprolegnia genome,which had an identity of 99% in sequence with that of other Saprolegnia strains.Additionally,17 samples from all over China were tested using this method and the SpHtp1 gene was present in 8 (47%) samples.The results indicated that the SpHtp1 gene is expressed specifically in S.parasitica,which can be used potentially for detection of Saprolegnia.