Vitaly Churkin dismissed the French initiative, which is to be put to a vote on Thursday, as a "publicity stunt" and said it would undermine efforts to find a political solution to the conflict in Syria.
It would be the fourth time Moscow has used its veto to block Western resolutions since the start of the conflict, three and a half years ago.
Moscow is Syrian President Bashar al-Assad's closest ally, and has provided him with diplomatic cover throughout the crisis.
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Western diplomats said it was uncertain which way China would vote Thursday, but several predicted it too would veto the resolution.
Since Syria is not a signatory to the International Criminal Court, it has fallen to the UN Security Council to decide whether to refer war crimes or crimes against humanity on its territory to the court.
Faced with mounting atrocities in Syria, Western powers and some of their allies are pressing for the resolution to dissuade the warring sides from engaging in new abuses.
The draft resolution denounces atrocities by government forces, by pro-government militias and by rebels fighting the regime.