Tlie a-card method, using a metal or plastic card buried underground for a considerable length of time to collect radon products by adsorption affect, and then using a special instrument to detect the a-radiation, is being increasingly applied to radioactive exploration for discovering very "faint radioactive anomalies. The collection of radon products on precipitators can be enhanced by applying a negative charge, but it complicates the equipment. The a-card method using electrostatic materials as precipitators solves this problem to a large extent. Akind of portable a-scintillator with a large area ZnS (Ag) scin-tillator has been developed by the authors. This method has been prelimina-rily applied in the search for uranium, underground water and cracks of dam. The comparison of it with other geophysical methods shows that it can be conveniently adopted and satisfactory results can be obtained with the advantages of high sensitivity (several times that of a-precipatator method), reliability, simplicity, efficiency and low cost.