In order to meet the demand of industrial production and scientific re search for simultaneous measurement of refractive index and temperature,a novel optical fiber sensor ha s been designed.The sensor is composed of no-core fiber (NCF) and long period fiber grating (LPFG) cascaded. In this sensor,NCF is sensitive to refractive index and LPFG is more sensitive to temperature.The sensor transm ission spectrum resonant Dip 3(excited by NCF) and dip 4(excited by LPFG) are selected to measure the ambient temperature and refractive index,respectively.The experiment shows that the center wavelength of Dip 3an d Dip 4has a good linear relationship with temperature,the temperature sensitivity was 9.46pm/℃ and 19. 88pm/℃,respectively.As the ambient refractive index varies in the range of 1.33-1.38,an excellent linear r elationship between the central wavelength of Dip 3and the refractive index,the refractive index sensitivity 102.80nm/RIU(refractive index unit). The central wavelength of Dip 4is not sensitive to the refractive index change. Using Dip 3and Dip 4temperature and refractive index sensitivity to construct sensitivity measuremen t matrix,the simultaneous measurement of refractive index and temperature is realized and eliminating cros s sensitivity.The designed sensor has simple structure,high refractive index sensitivity,low cost and good struc tural repeatability.It can meet the actual needs of the project.It can meet the actual engineering needs.