We prepared carbon nanospheres by pyrolysis of core cross-linked diblock copolymer micelles. Poly(ethylene oxide)-b-poly(4-ethynylstyrene) (PEO-PES) with a hydrophobic block having curable acetylenic groups was synthesized by atom transfer radical polymerization. The number-average molecular weight (M.) of the PES block was calculated to be 2200 from the peak area ratio of the PEO block to the PES block and the M. of PEO (5000). A micelle with the size of about 28 nm was prepared by dissolving PEO-PES in water (0.05 mg/mL). A micelle core consisting of PES blocks was cross-linked by the photoreaction of acetylenic groups. In the subsequent pyrolysis, the cross-linked core was carbonized and the PEO block of the shell eliminated, resulting in a carbon nanosphere with a diameter of about 8 nm. The FT-IR spectrum showed that all of the characteristic bands for the diblock copolymers disappeared after pyrolysis. The Raman scattering spectrum of the carbon nanosphere exhibited typical partially graphitic carbon characteristics, with a strong and relatively narrow band at 1590 cm(-1) and a broad band at 1350 cm(-1), corresponding to graphitic species (G-band) and disordered species (D-band), respectively.