This paper proposes a novel sensor scheme for simultaneously achieving temperat ure and surrounding refractive index (RI) based on a Sagnac loop composed of a long period grating ( LPFG) and polarization maintaining fiber (PMF).The LPFG and PMF are e mbedded in Sagnac fiber loop,and the Sagnac interference phase difference is sensitive to the surrounding RI thanks to the LPFG′s birefringence.The transmission dip formed by the LPFG and the interference dips formed by the whol e Sagnac fiber loop have different sensitivities to temperature and surrounding RI.Therefore,temperature and surrounding RI can be simultaneously measured by monitoring the wavelength shifts of the transmiss ion dip and the interferen ce dips.A dual-parameter testing device for temperature and surrounding RI is experimentally built,and has small source pow er perturbations by wavelength demodulation. The temperature sensitivity can reach 1.2nm/℃,and the surrounding RI sensitivi ty is 15nm/RIU.This proposed sensor with simple structure eliminates the cross-sensitivity of temperature and RI,has metallic pac kage to protect the LPFG and potential applications in the chemical and biological field.