An electrostatic discharge protection circuit, comprising: a first N-type transistor, comprising: a first gate terminal, coupled to a ground terminal; a first source electrode terminal, coupled to the first gate terminal; and a first drain electrode terminal; and a first base terminal, wherein the first gate terminal, the first source electrode terminal, and the first base terminal of the N-type first transistor are all coupled to the ground terminal; the ESD protection circuit further comprising a second N-type transistor, comprising: a second gate terminal, coupled to a metal pad; a second source electrode terminal, coupled to the second gate terminal; a second drain electrode terminal, coupled to the first drain electrode terminal; a second base terminal, wherein the second gate termnal, the second source electrode terminal, and the second base terminal are coupled to the metal pad; and a fifth electrode terminal, coupled to an isolation region (227, 228) of the second N-type transistor; and the ESD protection circuit further comprising a high-voltage tracing circuit, comprising: a first input terminal (In_1), coupled to the metal pad and configured to receive a metal pad voltage (V PAD); a second input terminal (In_2), configured to receive a supply voltage (VDDIO); and an output terminal (Out), coupled to the fifth electrode terminal, configured to output a high-voltage tracing voltage, wherein the high-voltage tracing voltage is larger than or equal to the metal pad voltage. a first N-type transistor, comprising: a first gate terminal, coupled to a ground terminal; a first source electrode terminal, coupled to the first gate terminal; and a first drain electrode terminal; and a first base terminal, wherein the first gate terminal, the first source electrode terminal, and the first base terminal of the N-type first transistor are all coupled to the ground terminal; a first gate terminal, coupled to a ground terminal; a first source electrode terminal, coupled to the first gate terminal; and a first drain electrode terminal; and a first base terminal, wherein the first gate terminal, the first source electrode terminal, and the first base terminal of the N-type first transistor are all coupled to the ground terminal; the ESD protection circuit further comprising a second N-type transistor, comprising: a second gate terminal, coupled to a metal pad; a second source electrode terminal, coupled to the second gate terminal; a second drain electrode terminal, coupled to the first drain electrode terminal; a second base terminal, wherein the second gate termnal, the second source electrode terminal, and the second base terminal are coupled to the metal pad; and a fifth electrode terminal, coupled to an isolation region (227, 228) of the second N-type transistor; a second gate terminal, coupled to a metal pad; a second source electrode terminal, coupled to the second gate terminal; a second drain electrode terminal, coupled to the first drain electrode terminal; a second base terminal, wherein the second gate termnal, the second source electrode terminal, and the second base terminal are coupled to the metal pad; and a fifth electrode terminal, coupled to an isolation region (227, 228) of the second N-type transistor; and the ESD protection circuit further comprising a high-voltage tracing circuit, comprising: a first input terminal (In_1), coupled to the metal pad and configured to receive a metal pad voltage (V PAD); a second input terminal (In_2), configured to receive a supply voltage (VDDIO); and an output terminal (Out), coupled to the fifth electrode terminal, configured to output a high-voltage tracing voltage, wherein the high-voltage tracing voltage is larger than or equal to the metal pad voltage. a first input terminal (In_1), coupled to the metal pad and configured to receive a metal pad voltage (V PAD); a second input terminal (In_2), configured to receive a supply voltage (VDDIO); and an output terminal (Out), coupled to the fifth electrode terminal, configured to output a high-voltage tracing voltage, wherein the high-voltage tracing voltage is larger than or equal to the metal pad voltage.