A new pure rotational Raman-lidar system for monitoring atmospheric temperature is presented. Instead of using the double grating monochromator, the system employs two high resolution spectral resolving channels,each of which is composed of a three-stage Fabry-Perot etalon combined with a filter with band width of 7nm. The transmitting light source is an injection-seeded Nd:YAG laser. This configuration can achieve a high rejection rate (10-10) to Mie-Rayleigh elastic scattering (at 532nm wavelength)，and has an extremely narrow receiving bandwidth (less than 10pm) for pure rotation Raman scattering of N2 with quantum numbers of ±6 and ±12 respectively. Therefore, the system effectively rejects the interference of background radiation and pure rotational Raman scattering of O2, and the measurement of daytime tropospheric temperature from a single Raman spectral line intensity ratio using the lidar system is made possible because of the narrow receiving bandwidth. The temperature measurement precision of this Raman-lidar is improved at the same time. At last, two_channels signals were simulated by using balloon-based sounding temperature profile. The simulation demonstrated the feasibility of this lidar for atmospheric temperature profile measurement.