The material of an epilithic diatom sample (including Berkeleya fennica), collected from Lake Qinghai, was processed using 10% HCl to dissolve all solid compound containing calcium, and then adding 30% H₂O₂ to oxidize and remove the organic matter of diatom cells. As a result, the clean diatom specimens can finally be obtained. Permanent slides were prepared well by using Naphrax^ mountant. The morphological characters of B. fennica were thoroughly studied under light and scanning electron microscope. The results show: (1) under light microscope, B. fennica possesses three characters: lanceolate valve outline, acutely rounded valve apices and markedly elongated central area. (2) Under scanning electron microscope, B. fennica possesses markedly elongated areolae which are close to the central area, and their lengths are equal to the ones of 2-4 normal areolae. (3) After consulting the literature and making comparisons between similar taxa, the current paper can confirm that the unique identifying character combination of B. fennica is the combination of the acutely rounded valve apices and the markedly elongated areolae close to the central area, by which the identity of B. fennica can be confirmed. Berkeleya fennica is reported for the first time in China in this paper.