gullible

gullible
/ˈgʌləbl; `ɡʌləbl/ adj
willing to believe anything or anyone; easily deceived 轻信的; 易受欺骗的
    He must have been pretty gullible to fall for that old trick. 他准是有点儿傻, 才落入那惯用的圈套.

牛津英汉双解词典