In this article an ultralow power CMOS temperature sensor are proposed. This sensor is applicable for wireless communication such as in RFID (Radio Frequency Identification), battery operated handheld device, wireless sensor network (WSN etc). This proposed circuits area and power consumptions are very less and compatible with wireless devices. It demonstrates the temperature measurement using the difference between the gate-source voltages of transistors operated in sub-threshold region that is proportional to absolute temperature (PTAT). By using the proposed scheme covers the wide range supply voltage of 0.6–3.0 V and total power consumption of 10.8nW at −50°C is obtained. The performance of the sensor is highly linear in the wide range of temperature −50° to 125°C. This is simulated using cadence virtuoso gpdk045 nm CMOS technology.