The invention relates to a steam-water separator for a freeze dryer, which comprises a cylindrical shell, two whirl plates, a steam-water filter screen and a semicircular baffle plate, wherein the two whirl plates, the steam-water filter screen and the semicircular baffle plate are arranged in the inner cavity of the shell from top down; the top surface of the shell is provided with an exhaust hole and the lower part of the lateral surface of the shell is provided with a water outlet; the bottom part of the shell is provided with a steam-water pipe extending into the inner cavity of the shell, the steam-water pipe comprises a straight pipe section and a bent pipe section integrally formed with the straight pipe section, the bent pipe section extends spirally upward along the central line of the shell till the outlet end of the bent pipe section is positioned under the baffle plate and the central line of the outlet end of the bent pipe section is parallel to a tangent line passing through an intersection point of the diameter line of the baffle plate and the surface of the shell; and the two whirl plates are both in an arch shape, the major arc edges of the two whirl plates are alternately connected with the inner wall of the shell and the two chord edges of the two whirl plates are parallel. The separator has the advantages of obvious steam-water separation effect, simple mechanism, easy manufacturing, low cost and the like.