In this paper, the effects of refractive index (RI) of surrounding medium and ambient temperature on the transmission characteristics of a long period grating (LPG) are experimentally analyzed. The spectral behavior of LPG is investigated when the ambient index is higher or lower than that of the cladding material. The results show that the refractive index sensitivity of lower order attenuation bands is very low compared with that of the highest order attenuation band. But in the case of temperature, the lower order attenuation bands of the LPG can also exhibit good sensitivity like the higher-order bands.