Abstract: The analytical solution of the mixing efficiency of the lobed mixer,in relation to that of the splitter mixer in the same cross-section area of outlet,was proposed by using the circular streamlines model,the planar diffusion flame model and the slender-body approach etc.,based on thoroughly study of the mixing mechanism of the lobed mixer.Then,the mixing efficiency of a practical turbo-fan engine lobed mixer was calculated in four flying cases.The results show that this analytical solution method is reliable and also applicable to the practical engineering calculation.