We reported a species of Mallomonas collected from Yichun City, Heilongjiang Province. Its main characteristics, such as scales and bristles, were observed by transmission electron microscope and scanning electron microscope. And a phylogenetic tree was constructed based on the SSU rDNA and LSU rDNA gene sequences. Combining morphological characteristics with molecular biological data, we identified this species as a new record species in China and Asia——Mallomonas intermedia. The systematical relationship between M. intermedia and other species which belong to the other series of the same section and its world distribution and dispersal were also discussed. This study provided new data for the geographical distribution of M. intermedia and the dispersal of Chrysophyta and other microalgae.