A low-cost, compact, and lossless temperature sensor based on a twin-core fiber (TCF) is demonstrated and manufactured by splicing two single-mode fibers to the ends of a TCF. The extinction ratio of the comb transmission spectrum is bigger than 15 dB, and the temperature sensitivity of the coupling angle is –0.02 rad/(oC.m) at –30–90 oC and –0.032 rad/(oC.m) at 90–175 oC. Finite element method is used to calculate the supermodes of the TCF, and the result agrees well with the experiment.