Abstract: To determine relative molecular weight of astragalus polysaccharides (APs), we used Shodex GS620 gel permeation chromatographic column and differential refraction detector (GPC-RI) with dextran as a reference. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and GPC combined with multi-angle laser light scattering detection (GPC-MALLS) were also used.GPC-RI measure showed four peaks of APs, with the M_w of 1 380 000, 231 000, 18 000, and 480, respectively. Three main peaks were found by GPC-RI-MALLS with the M_w as 1 148 000, 180 000, and 43 000, respectively. Strong signals in 155 000 and 18 000 were detected by MALDI-TOF-MS, which also indicated the sugar moieties of the APs as hexoses. From our study, we found that the GPC-RI method with universal correction is most suitable for M_w determination of the APs. Nevertheless, the three methods should be combined and contrasted with each other to obtain accurate information in research of polysaccharides from Chinese medicine.