HPLC analysis for paralytic shellfish poison (PSP) in shellfish foods has now become a current method in the world, in which PSP standard is necessary. Unfortunately, commercial PSP standard has now become difficult for handling in china, as some purification technique of PSP has not been still breached, and the PSP substance has now been recognized into the list of chemical weapons. Preparing independently some PSP standard is necessary and will be a good way for solving the standard substance problem in china.  In this paper, extraction and purification of PSP was discussed, using a poisoned scallop sample as a material. The total toxicity of the crude PSP extract solution was 6 170 MU, while using acid 80% ethanol as an extractant. From the crude extract, PSP was purified via ultrafiltration, Bio-Gel P-2 column chromatography and BioRex 70 column chromatography, and a purified toxin with amount of 2 100 MU was obtained. The result of chromatography showed the toxin mainly contained gonyautoxin group (GTX1-4). HPLC analysis showed that all of the peaks is very sharp and clear, in which the ratio of GTX1, GTX2, GTX3 and GTX4 was 2∶4∶14∶1 (calculated as the ratio of peak area on HPLC), indicating that GTX3 is the major PSP composition in the poisoned scallop sample, and the purified toxin is available using as a standard for HPLC analysis. From the results of experiments, the technique for preparing PSP standard is effective and successful. In the other hand, the stability of the purified toxin was discussed, through comparing the HPLC analysis between the native toxin and that of the one treated with 0.1 mol/L HCl.