Mass spectrometric profiling using ProteinChip and magnetic beads has rapidly grown over the past years, particularly to generate serum profiles for cancer diagnosis. The molecular weights of these distinguishing peaks are usually under 30 kDa. To identify those low molecular weight proteins and peptides is important for specific assays to be developed and increases biological insight. In this study, low molecular weight proteins and peptides from serum were purified by a combination of weak cation exchange magnetic beads and high performance liquid chromatography. The purified proteins and peptides were analyzed by 1D SDS PAGE, SELDI and LC-MS/MS. 246 proteins were identified from the HPLC fractions by LC-MS/MS. 95(38.62%) proteins were first identified in serum compare with Sys-BodyFluid database. 11(11/96) proteins were documented cancer associated proteins. We also observed about 109 proteins/peptides in SELDI mass spectrum, and 13 of the SELDI features were identified.