The invention relates to a manufacturing method of a graphene-porphyrin modified electrode and application of the electrode, aiming to solve the problems of complex operation, long time and relatively high price in the conventional method for detecting the content of ascorbic acid in a living body. The method comprises the following steps: I, preparing pre-oxidized graphene; II, preparing a graphene oxide solid; III, preparing acyl-chlorinated graphene; IV, preparing tetraphenylporphyrin; V, preparing 5-(4-nitro)-10,15,20-triphenyl porphyrin; VI, preparing 5-(4-amino)phenyl-10,15-20-triphenyl porphyrin; VII, preparing a pure manganese porphyrin coordination compound; VIII, preparing a functional composite material of graphene oxide and porphyrin; IX, modifying a glassy carbon electrode. The modified electrode has excellent interference resistance, stability and reproducibility, and can be taken as a biosensor for detecting ascorbic acid in practical samples.