Abstract: The optical fiber preform waste powder with the oil absorption value of 1.64 mL/g was acid?鄄washed with oxalic acid and then calcined at 600 ℃ to remove the impurity fraction，and white carbon black with oil absorption value of 2.1 mL/g was obtained.In order to explore the mechanism of the process，the product was characterized by LDSA and FT-IR.It was found that the particle size of the powder was significantly increased compared with the original waste powder，and there was a new infrared absorption peak at 1 480 cm-1，which was predicted to be a C—O stretching vibration peak in the CO3 group. The model of the bond structure between the powder particles was obtained by Gaussian 09 program simulation.The infrared spectrum simulation of the model was basically consistent with the experimental ones，which supported the prediction of the attribution of the new absorption peak.The reason why the oil absorption value of the optical fiber preform waste powder was improved after oxalic acid pickling and calcination at 600 ℃ may be that the oxalic acid was esterified with the hydroxyl groupson the surface of different particles，and then the CO was removed at a high temperature to form a secondary structure of three?鄄dimensional network which was composed of silica particles being connected with CO3 groups，which not only increased the particle size but also improved the pore structure.Therefore，the oil absorption value of the product was improved.

Key words: optical fiber preform waste；oxalic acid；acid?鄄washing；white carbon black；oil absorption value