The invention relates to the field of protein, in particular to a plurality of milk-derived biological active peptides such as QNIP, QQPV, GEIVE, VSKVK and PYPQRD derived from beta-casein. According to an in vitro anti-oxidation experiment and an in vitro immune function promotion experiment, the biological active peptides have different anti-oxidation biological activity and cellular immunity promoting activity; a research result shows that the five milk-derived biological active peptides as one kind of small molecular substances have a potential senescence delaying function; and besides, a digestion simulation experiment result shows that the five biological active peptides are stable under common animal body digestion conditions, cannot be further degraded, can be directly absorbed and used by animal bodies to play the biological activity function, and have great significance in the aspect of development of dairy products, healthcare products and drugs with functions of antioxidation, immune function strengthening and senescence delaying.