Here, a novel iron-porphyrin-based covalent organic framework (COF) was synthesized and applied for electrochemical sensing HO and pH which involved in many biological processes. The COF was obtained by post-modification of porphyrin-based COF (COF) which was firstly synthesized by aldehyde-ammonia condensation reaction between 1,3,5-benzenetricarboxaldehyde and 5,10,15,20-tetrakis(4-aminophenyl)-21H,23H- porphine. The COF was proved to be regular and uniform spherical particles with diameter about 1 μm, as well as possessed good crystalline structure and abundant micropores of about 1.4 nm. The resulted COF after post-modification with Fe maintained the original shape and crystalline structure of COF, while the micropores decreased to be about 0.89 nm. Electrochemical results indicated that the synthesized COF had good electrochemical redox and proton activity owing to iron-porphyrin, enabling to simultaneously be used as mimic peroxidase to catalyze the reduction of hydrogen peroxide (HO) and evaluate pH using current and potential as signal, respectively. The prepared sensor showed good performance for HO detection from 6.85 nM to 7 μM with the detection limit of 2.06 nM (S/N = 3), and pH test from 3.0 to 9.0. This work demonstrated that the iron-porphyrin-based COF could be used as a mimic peroxidase to apply in biological fields.