A fiber sensor based on photonic cryst al fiber (PCF) and core- offset structure is proposed.It is manufactured by splicing PCF and single mode fiber (SMF).Transmit ting through the core-offset structure,the light is coupled into the core and c ladding of PCF.The modes of core and cladding interfere when the phase condition is achi eved.The dips of transmission spectrum can be used to measure the variations of temperature and r efractive index. Experimental results show that temperature sensitivity and refractive index sens itivity are －8×10－3 nm/℃ and 102nm/RIU,respectively.Then alcohol is filled into the PCF and the sensor with the same structure is manufactured.Experimental results show that the temperature sensitivity reaches －1.008nm/℃,which improves by 123times.The sensor has the advantages of easy fabrication and simple operatio n,and it can be widely applied in biological and physical sensing fields.