Swine plays a significant role in livestock agriculture. As a linkage between sows and piglets, porcine milk is crucial for the health of newborn piglets. Free milk oligosaccharides (MOs) are kinds of important bioactive substance in mammalian milk. However, little is known about the component and function of the porcine MOs (PMOs). In this study, a hydrophilic interaction chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (HILIC-Q-TOF MS) system was utilized to profile the PMOs. Forty-one distinct PMOs were identified totally in three breeds of sows. The PMOs were highly sialylated (similar to 30%) and fucosylated PMOs (1-3%) were monitored at low levels. The most abundant oligosaccharide was a trisaccharide (Hex(3)) which contributed over 50% of the total PMOs abundance. Comparison of free MOs profiles revealed heterogeneity and variations among individuals and different breeds of sows, however, the MOs variation among breeds was limited even minor than that among individuals. Furthermore, most PMOs contents were higher in colostrum and decreased in the early lactation, but a few kinds increased at last. Different oligosaccharides had different patterns during lactation. Overall, these observations showed a more detailed PMOs library and would contribute to the exploration of influence of PMOs on piglets' health.