The invention discloses an furan resin with easy collapsibility used in casting and a preparation method, which is made from a modified rosin. The addition amount of the rosin is 5 to 37 wt percent and is calculated by the total amount of furfuryl alcohol. In the process of synthesizing the furan resin for casting, the modification of the furan resin by adding the rosin can accelerate the heat decomposing speed of the resin; thus the collapsibility of the resin sand is improved and is more suitable for the requirements of the casting production. In the first reaction step in the preparation method when synthesizing the rosin modified furfuryl alcohol, the reaction PH value is 1.0 to 3.0, and the reaction temperature is at 70 DEG C to 90 DEG C; in the second reaction step when synthesizingthe furan resin with easy collapsibility, the mol ratio of carbamide and formaldehyde is 1:1.2 to 1:2.4. The obtained easy collapsed furan resin is specialized in casting technology field, and the collapsibility of the resin sand is improved by 30 to 60 percent.