Herein, we report nonaqueous synthesis of metal cyanamide semiconductor nanocrystals, including Ag2NCN nanorods (NRs), ZnNCN NRs and PbNCN nanoparticles. The as-prepared Ag2NCN NRs with a band gap of 2.35 eV are applied as photocatalysts for water oxidation. Their oxygen evolution rate (280.7 μmol h-1 g-1) is much higher than that of Ag2NCN microcrystals (24.0 μmol h-1 g-1).