A surface plasmon resonance (SPR) sensor based on side-polished fiber is fabricated by coating a thin gold film on the polished zone. The characteristics of the sensor for ambient refractive index and temperature are tested. The results show that the resonance dip shifts to longer wavelength as the ambient refractive index is increased and shifts to shorter wavelength as the temperature is increased. The average sensitivity of resonance wavelength to variation in refractive index is 4.1×103 nm/RIU (RIU is the unit of refractive index). Moreover, a linear sensitivity of resonance wavelength to variation in temperature reaches 0.36 nm/℃. The fiber optical SPR sensor, possessing stronger resistance to temperature drift and higher refractive index sensitivity, can play an important role in biochemical sensing.