【Objective】Different expression profiles of polypeptides in follicle fluid from superovulated cattle and calves were studied in order to provide references for further research on follicle fluid of calves and in vitro oocyte culture system of calves. 【Method】The matrix-assisted laser desorption ionization mass spectrometry （MALDI-TOF MS）was used to analyze the peptide fragments in follicular fluid of superovulated cattle and calves. Based on signal peak information of polypeptide， protein search was conducted in MASCOT database. 【Result】The models of polypeptide expression profiles of the two groups were successfully established， respectively. There were 30-40 peak signals in cattle group， and 60-80 peak signals in calves. By comparing the peak lists from the two different samples， it was found that 2 specific peaks of 1218.58 and 1509.77 m/z appeared in cattle group， similarly， and 1 specific peak of 953.54 m/z in calf group. At last， MASCOT library was used to search the information of polypeptides， and then some proteins related to these polypeptides information were gained. The results showed that 18 kinds of proteins existed in cattle group， and 11 kinds of proteins in calves. 【Conclusion】The results showed that the polypeptide information peak quantity of calf follicular fluid protein was higher than that of adult cattle， while the total number of proteins in follicle fluid from the calves was less than that of the adult cattle group， which could be one of reasons why the developmental competence of oocytes from calves was poorer than that of adult cattle.