The present study is a comparative study on preliminary characterizations and immunostimulatory activities of water-soluble polysaccharides (WSP) from newly hybrid Amomum villosum and its female parent. First, two kinds of WSP were extracted, respectively from the newly hybrid A. villosum called Spring No.1 (WSPH) and its female parent-Longfruit No.2 (WSPP). Then, the differences of preliminary characterizations and immunostimulatory activities in vivo for these two WSP samples were compared. Experimental results showed that WSPH and WSPP had the same monosaccharide composition, and similar ultraviolet and infrared spectra characteristics of polysaccharides, while their immunostimulatory activities, in terms of the weights of spleen and thymus, pinocytic activity and the level of serum hemolysin, showed no significant differences between the groups treated with WSPH and WSPP, respectively. Combined with the findings from other studies in our research group, these results suggested that this novel hybrid could be an acceptable alternative for cultivation of A. villosum. Copyright © 2015 Elsevier B.V. All rights reserved.