Lanzhou lily (Lilium davidii var. unicolor) with symptoms of severe fasciation or dwarfing was observed in the central region of Gansu province, and the disease caused a serious loss in production of the bulb edible crop. In order to determine possible virus infections involved in the described disease, a set of enzyme-linked immunosorbent assays and immunoelectron microscopy had been performed to test the naturally infected plants. A mixed infection which includes Lily symptomless virus (LSV: Flexiviridae, Carlavirus), Cucumber mosaic virus (CMV: Bromoviridae, Cucumovirus) and Lily mottle virus (LMoV: Potyviridae; Potyvirus) has been confirmed by serologic and morphologic evidences. The subsequent thin sectioning observation with a transmission electron microscope on different tissues from infected samples showed that cytopathologic damages happened. Total RNA extracted from different tissues of infected plants was used in the Northern-blotting assays with probes of coat protein gene of each virus, then hybridization data showed a symptomatic infection of related virus. Thus, the study gives reliable serologic, morphologic, cytopathologic and molecular evidences for the diagnosis of the systemic infections. This study is hoped to be useful in prevention of certain viral diseases and to increase the quality and production of this crop in the future.