The invention relates to a method for separating and extracting stem cells from a placenta, umbilical cord or adipose tissue, which comprises the following process steps: firstly mixing the placenta, umbilical cord or adipose tissue and a cell maintenance fluid according to the proportion by weight of 2.5-4:1, putting the mixture into a tissue crushing barrel, adding collagenase after crushing, uniformly mixing, hatching at the temperature of 37 DEG C, filtering, adding a precipitator, sucking a supernatant fluid after settling, centrifuging, removing the supernatant fluid, adding concentrated cells into a liquid of diatrizoate sodium-ficoll 400#, then centrifuging, collecting 10-15 ml of intermediate cell layer, washing with the cell maintenance fluid, counting the collected cells, and providing the cells for clinical use when the cell survival ratio is more than or equal to 95 percent. The invention not only realizes the separation and the extraction of all stem cells from the placenta, umbilical cord or adipose tissue, but also realizes industrialized production, and enables doctors to conveniently, safely and canonically obtain the adult stem cells in clinic and use the adult stem cells for treating the diseases of patients as using medicaments, thereby solving the bottleneck problem of difficult obtainment of adult stem cells in clinic and popularizing a cell treatment technology.