A temperature detecting circuit and method thereof, adapted to a voltage converter circuit which includes a current detecting circuit having a detecting output port outputting a current detecting signal proportional to an output current of the voltage converter circuit, includes: a current signal processing unit, having a signal input port coupling to the detecting output port, a first detecting output port generating a first processing signal with a first temperature coefficient, a second detecting output port generating a second processing signal with a second temperature coefficient, wherein the first and the second processing signals are proportional to the current detecting signal; and, a temperature calculating unit, receiving the first and the second processing signals and performing calculation to derive a temperature value.