▎ 摘　　要

In this paper, one contrast experiment is reported. Two identical back-gate graphene transistors samples are fabricated. One is washed by developer for 3 minutes and washed by deionized water for 10 seconds. The other is washed only by water for 10 seconds. For the first sample, the Dirac point voltage of a graphene transistor decrease 35 V, while that of a graphene transistor in the second sample increase more than 17 V. This phenomenon indicates that developer can decrease P-doping of graphene, and reasons have been analyzed. While the first sample is exposed in atmosphere for a week, Dirac point voltages are still less than those before washed. This result shows that the influence of developer has not disappeared.