A new approach for simultaneous strain and temperature measurement using a single fiber Bragg grating has been reported in this paper. The fiber Bragg grating used for simultaneous strain and temperature measurement is written on the joint of two different fibers, and has two reflection-peaks at different wavelength, which have different temperature response because of the different thermo-optic coefficients for the two fibers. By measuring wavelength shift of the two peaks, strain and temperature can be determined simultaneously.