Raman distributed temperature sensing (RDTS) is widely used in many fields. The system configuration, devices, and data processing methods have been well studied and improved, but research on sensing fiber itself is rare. We design a multimode fiber for RDTS based on experimental results from a series of conventional multimode fibers. The optimized multimode fiber offers temperature sensing at a distance less than 10 km. It has a much larger nonlinear effect than conventional multimode fibers, so the spontaneous anti-stokes signal under the same optical input is 1.5 to ∼ 2.4 times higher. Its loss and dispersion within the wavelength range from 1400 to 1650 nm is acceptable. Therefore, under the same system configuration, a higher anti-stokes signal is received by the data acquisition card, which makes signal acquisition and processing easier and improves temperature sensitivity, accuracy, and resolution without sacrificing other characteristics, such as spatial resolution and measuring distance.