This paper proposes a novel second-order temperature-compensated CMOS current reference which exploits a new self-biased current source for first-order temperature compensation and a resistor-free widlar current mirror for second-order temperature compensation. Moreover, by deriving the temperature coefficient (TC) of the reference current, the temperature compensation condition equations together with a design method of minimizing the thermal drift in a required temperature range are presented. Based on these, the circuit is designed in a standard 0.18 μm CMOS process and achieves a very low TC of only 16.9 ppm/°C in a temperature range between -40°C and 120°C, with 1 μA reference current at 27°C. Besides, the current reference can operate at supply voltage down to 1.3 V, with a good supply regulation of 0.5%/V. At 27°C, its power consumption is 8.93 μW.