B3 1343 + 451 is a distant ( z = 2.534 ) and bright flat-spectrum radio quasar observed in the γ -ray band. The results from the multiwavelength observations of B3 1343 + 451 with Fermi-LAT and Swift are reported. In the γ -ray band, strong flares were observed on 05 December 2011 and on 13 December 2009 when the flux increased up to (8.78 ± 0.83).10-7 photon cm-2 s-1. The hardest photon index Γ = 1.73 ± 0.24 has been observed on MJD 58089 which is not common for flat-spectrum radio quasars. The analysis of Swift XRT data shows that in 2014 the X-ray flux of the source increased ~2 times as compared to 2009, but in both periods the X-ray emission is characterized by a hard photon index of ΓX-ray = 1.2-1.3. During the γ -ray flares, the shortest flux halving timescale was ~2.34 days, implying the emission had been produced in a very compact region, R ≤ δ ct /(1 + z) = 3.43.1016 cm (when δ = 20 ). The spectral energy distribution of B3 1343 + 451 is modeled during the quiescent and flaring periods assuming a compact emitting region outside the BLR. It is found that the flares can be explained by only changing the bulk Lorentz factor of the emitting region without significant modification of the emitting electron parameters and luminosity of the jet.