The Wittig reaction was carried out on cyanomethylenetriphenylphosphorane (I) and α-bromocyanomethylenetriphenylphosphorane (IV) as the phosphoranes and 5-nitrofurfural (IIa) as the aldehyde, and also the reaction of I with furfural (IIb), 5-methylfurfural (IIc), and 5-bromofurfural (IId). Examinations were also made on the solvent effect and the salt effect of Lewis bases on the formation ratio of cis and trans compounds. Identification of the components was made through elemental analyses and the infrared and NMR spectra, and the formation ratio of cis-and trans-olefins was determined by gas chromatography. It was thereby found that the cis compound was formed in larger amounts in benzene solvent.