The drilling construction was difficult in Tongling copper-gold polymetallic ore concentration area of Anhui, where caves and fissures developed; long construction period and high cost were caused by serious drilling fluid loss in the drilling process. But good result was achieved by the preparation of asphalt balls which were used in ZK6616 hole for limestone and fractured marble formations plugging. This case can be a good reference to those formations where the conventional plugging means have no effect; and at the same time, it has an important significance for the loss zone drilling.