Quasi-two-dimensional perovskites, with spectral tuning property, have opened up vast application prospects in the field of optoelectronic devices, especially in blue perovskite light-emitting diode (PeLED). However, relatively high density of defect states usually results in nonradiative recombination loss due to unexpected carriers capture at prolonged transport, which limits high-performance PeLED. Here, we propose a method for preparing pure-blue PeLED using bifunctional amide molecules to modulate crystallization kinetics. This strategy inhibits the formation of the n = 1 phase and simultaneously passivates defects with the bifunctional groups, thereby reducing the occurrence of nonradiative recombination. The external quantum efficiency of the pure-blue PeLED fabricated using this strategy is significantly enhanced, reaching 9.7% at 478 nm, which is about 7 times higher than that of the control device. This work provides a novel strategy on the selection of bifunctional passivators for perovskites.