Seven derivatives of 2,3-alkyl substituted N-cyanoaziridine were stereoselectively prepared from alkyl substituted alkenes and cyanamide. NMR spectral property and conformation of N-cyanoaziridine were analysed. Protons(3.34 ppm) at 2,3 position of N-cyanoaziridines are significantly deshielded in case of cyclopentyl fused N-cyanoaziridine. These protons are getting more anisotropically shielded with increasing the fused carbocycle size of N-cyanoaziridine. Therefore chemical shift for these protons are upfield shifted to 2.80 ppm in case of cyclooctyl fused N-cyanoaziridine. Their ED$_{50}$ values aganist L$_{1210}$, cell in vitro were evaluated as 0.5~8.0 $mu$g/ml. Conformation of carbocycle of fused N-cyanoaziridine is more important to their cytotoxicity than the increment of the strain energy of 3-membered ring.