The invention discloses a capacitive cement-based humidity sensitive element and a preparing method thereof. The element is composed of a cylindrical cement-based blank and ring-shaped electrodes, wherein the ring-shaped electrodes are located at the positions which are spaced from two end openings of the cylindrical cement-based blank by 10-20 cm and are inwards parallel to the two round faces, the cylindrical cement-based blank and the ring-shaped electrodes are bonded in a sealed mode through copper powder mixed with conductive adhesive, and the ring-shaped electrodes are connected with a wire. The element is good in durability, a certain quality of porous adsorbing materials are doped, the element makes close contact with a building and can synchronously detect the relative humidity in a building structure in time, and measurement results are timely and reliable. Durability of the building structure will not be affected by burying the measuring element, the humidity sensitive element is low in price, and therefore construction cost can be reduced greatly.