This work presents a novel 3D carbonized wood-based integrated electrochemical immunosensor for ultrasensitive detection of procalcitonin (PCT) antigen at picogram level, achieving a wide linear detection range for PCT concentrations range from 0.05 to 90 pg mL with a low detection limit of 0.014 pg mL (S/N = 3), outperforming the previous reports. 3D carbonized wood as a new immunosensor matrix is used for electrochemical PCT biosensing, improving the stability of electrode and overcoming the disadvantages of traditional glassy carbon electrode (GCE). It obtained an excellent detection result, due to it has abundant mutual crisscross microchannels that promote the reactants and electrons transfer, greatly amplify the current signal. This novel sandwich-type electrochemical immunosensor is composed of 3D carbonized wood, carboxylic multi-walled carbon nanotube (cMWCNT), Au@CoO core-shell nanosphere and Au/single layer nitrogen-doped graphene (Au/SL-NG), when it is applied for PCT detection in real clinical samples, it exhibits high accuracy same as enzyme-linked immunosorbent assay (ELISA) method.