Pollen allelopathy is a kind of special allelopathy that may inhibit pollen germination and seed set of sympatric species which receive allelopathic pollens. The present study focused on assessing potential effects of pollen extract from Stellera chamaejasme on pollen germination and seed set of several sympatric species. It also included in-vitro research on the effects of pollen extract from S. chamaejasme on six sympatric species, namely Gentiana macrophylla var. fetissowii, Gentianopsis paludosa var. paludosa, Gentiana squarrosa, Halenia elliptica var. elliptica, Ranunculus tanguticus var. tanguticus and Potentilla anserina var. anserine, as well as pollen from itself. Field experiments on the effects of pollen extract with the same regime of concentration on the seed set of four sympatric species namely G. macrophylla, G. paludosa, G. squarrosa and H. elliptica, were also carried out. The result of in-vitro experiments showed that pollen of S. chamaejasme was not autotoxic, whereas the pollen germination of all the sympatric species decreased nonlinearly as the concentrations of pollen extract from S. chamaejasme was increased. The pollen extract of three-grained pollens of S. chamaejasme in general, inhibited 50% of pollen germination of most of the focal species. The result from field experiments showed that the seed set of four sympatric species decreased nonlinearly as the concentration of pollen extract from S. chamaejasme was increased. It can be inferred that S. chamaejasme may therefore have negative impact on sexual multiplication of the sympatric species through pollen allelopathy. However, these species could sustain themselves by avoiding pollen allelopathy of S. chamaejasme through either seasonal divergence or diurnal flowering phonologies and through asexual reproduction.