Abstract: In order to satisfy ¹⁴C measurement with the new developed 200 kV single stage electrostatic accelerator mass spectrometer, the sample preparation processes for ¹⁴C were investigated. The graphitization experimental conditions for H₂-Fe, Zn-Fe and Zn-H-Fe methods were optimized on self-designed ¹⁴C sample preparation system. The beam current of ¹²C^- for all prepared samples can reach 15-40 μA and its stability is better than 0.2%. The ¹⁴C measurement shows that the lower particle number ratio of ¹²CH⁺ -¹³C and ¹²C benefits the high sensitivity and miniaturization of device. The result also shows that the Zn-Fe method can depress the particle number ratio of ¹²CH⁺ -¹³C and ¹²C for the samples with the carbon content less than 1 mg, while, for the carbon content among 1 mg to 5 mg, the Zn-Fe and Zn-H-Fe methods have the equivalent effect. For above preparation methods, the yield of carbon can reach more than 95% for the carbon content of 100 μg-5 mg. Moreover, through blank sample measurement it is proved that the cross contamination during the sample preparation can be avoided.