The invention relates to a moisture measuring instrument with high reliability which comprises a main body, a sealing plate, a storage box, a bottom plate, a weighing device, two supporting blocks andfour fixing blocks, and further comprises an impurity removal mechanism and two stirring mechanisms, wherein the impurity removal mechanism comprises a fixing box, a heating rod, two exhaust pipes and two impurity removal assemblies. The stirring mechanism includes a motor, a screw rod, a rotating shaft, a first bearing, a second bearing, a sliding block, a stirring assembly, a connecting rod andtwo supporting rods. Through the impurity removing mechanism, the function of removing impurities from air entering the main body is achieved, the situation that dust adheres to materials, and consequently the weight of the materials is increased is avoided, thereby avoiding affecting the detection accuracy, the stirring mechanism realizes the function of stirring the materials inside the storagebox, the situation that the materials are accumulated together and cannot be fully dried is avoided, and therefore the influence on the drying efficiency is avoided.