Abstract: The achene shape and pericarp micro-morphology of 18 species of Cyperus in Shandong were observed and studied under scanning electron microscopy (SEM). Results showed that the Cyperus achenes were ellipsoidal-,ovoid- and obovoid-triangular with a columnar or conoid short-beak at the apex. The pericarp micro-morphology was classified into four types,viz reticulate-verruciform,reticulate,verruciform and irregular raised ornamentation. Although micro-morphology classification did not exhibit a relationship with traditional macro-morphology classification,it found obvious differences among species similar in morphology within Cyperus and also provided evidence of circumscription among species. Pericarp micro-morphology supported the opinion of attributing Juncellus,Mariscus and Torulinium to Cyperus.