The Pyrola dahurica, an indicator of mixed conifer broad-leaved forest, is an important medicinal species in northeastern China. The mechanism of cold hardiness for this evergreen species is not well known. To explore its cold hardiness during winter seasons, we measured contents of MDA and osmoregulatory substances (i.e. soluble sugar, soluble protein and proline) in the rhizomes and leaves of Pyrola dahurica in two stages: early stage of snow cover (ESSC: from October to December in 2005) and late stage of snow cover (LSSC: from March to April in 2006). The results showed that the MDA content increased at the beginning, and decreased gradually as the winter proceeded, suggesting that the degree of membrane injury decrease due to coldness conditioning. Compared with that in the leaves, the MDA content in rhizomes was lower in ESSC and higher in LSSC. The contents of soluble sugar and protein increased with the temperature decreasing in ESSC, peaked in the middle of November, and decreased afterwards; while that of proline presented an opposite trend. In the following spring as temperature was rising and snow melting, the contents of osmoregulatory substances (soluble protein and free proline) sharply increased, while the content of soluble sugar dropped gradually. The soluble protein content was strongly positively correlated to the free proline content. Whether in ESSC or in LSSC, the content of soluble sugar in rhizomes was lower than that in leaves, while the contents of soluble protein and proline in rhizomes was higher than those in leaves. We concluded that the Pyrola dahurica adapted low temperature winters by adjusting the contents of osmoregulatory substances in its leaves and rhizomes.