Limited energy source dominates the use of sensor system, especially for outdoor environment monitoring. This paper presents a self-sustaining moisture and temperature monitoring system using soil energy. The proposed sensor system includes the soil energy cell, which can produce 60~100μW, a temperature/humidity sensor, a Bluetooth low-energy transmitter, a microcontroller and a custom low-power capacitive sensor readout silicon chip. The system is demonstrated measuring temperature and air moisture changes directly using inexpensive and renewable soil energy without external power supply. The capacitive sensor readout chip is only consumes 3μW. The total power consumption of the wireless temperature and air moisture monitoring system is 20μW and 1mW in the sleep mode and the active wireless data communication operations, respectively. This technology enables remote field environment monitoring with less labor-intensive work and battery replacement.