Abstract: A new multilayer blazed reflective grating is shown.Using thin-film technology,the blazed reflective grating's diffraction property and reflectivity property have been improved greatly.Making use of these properties,the gain narrowing in femtosecond lasers is restrained.The calculation result and experiment result show that using this new grating to broaden seed pulse has many advantages:the loss of seed pulse energy is less,the efficiency of broadening is high,the gain narrowing is attenuated much.Furthermore it can make experiment easier and convenient for integration.