An implantable micro-biosensor adapted to be implanted under skin of a body to continuously monitor a physiological parameter of an analyte in a biological fluid of the body, said implantable micro-biosensor comprising: a substrate including an implanting end portion which is elongated in a longitudinal direction and which is configured to be implanted under the skin along an implanting direction perpendicular to the skin; a first electrode which is disposed on the substrate and used as a counter electrode, and which includes a front portion and a rear portion both disposed at said implanting end portion, wherein said front portion extends along the longitudinal direction, and said rear portion extends along the longitudinal direction and away from said front portion, a sensing section of said first electrode at least including said front portion; a second electrode (5, 9) which is disposed on said substrate and spaced apart from said first electrode, and which includes a sensing section (50, 90) disposed at said implanting end portion and having an area less than that of said sensing section of said first electrode; a third electrode which is disposed on said substrate and used as a working electrode and which includes a sensing section disposed at said implanting end portion; and a chemical reagent layer which at least covers said sensing section of said third electrode, said third electrode being able to selectively cooperate with said first electrode or said second electrode (5, 9) to measure a physiological signal in response to the physiological parameter of the analyte, wherein said first electrode and said second electrode (5, 9) are disposed on one surface of said substrate, and characterised in that said third electrode is disposed on the other surface of said substrate opposite to said one surface of said substrate on which said first electrode is disposed and further characterised in that said front and rear portions (40a, 40b) of said first electrode being disposed respectively proximate to two adjacent sides of said second electrode (5,9). a substrate including an implanting end portion which is elongated in a longitudinal direction and which is configured to be implanted under the skin along an implanting direction perpendicular to the skin; a first electrode which is disposed on the substrate and used as a counter electrode, and which includes a front portion and a rear portion both disposed at said implanting end portion, wherein said front portion extends along the longitudinal direction, and said rear portion extends along the longitudinal direction and away from said front portion, a sensing section of said first electrode at least including said front portion; a second electrode (5, 9) which is disposed on said substrate and spaced apart from said first electrode, and which includes a sensing section (50, 90) disposed at said implanting end portion and having an area less than that of said sensing section of said first electrode; a third electrode which is disposed on said substrate and used as a working electrode and which includes a sensing section disposed at said implanting end portion; and a chemical reagent layer which at least covers said sensing section of said third electrode, said third electrode being able to selectively cooperate with said first electrode or said second electrode (5, 9) to measure a physiological signal in response to the physiological parameter of the analyte, wherein said first electrode and said second electrode (5, 9) are disposed on one surface of said substrate, and characterised in that said third electrode is disposed on the other surface of said substrate opposite to said one surface of said substrate on which said first electrode is disposed and further characterised in that said front and rear portions (40a, 40b) of said first electrode being disposed respectively proximate to two adjacent sides of said second electrode (5,9).