In order to improve the mixing performance of fan bypass and CDFS (core driven fan stage) bypass, a innovative configuration of FVABI (front variable area bypass injector) with jet mixing enhancement was proposed. Numerical simulation was performed to investigate mass flow rate characteristic, flow mixing and total pressure loss of FVABI configuration with lobed mixer. Compared with the baseline configuration, the predictions are discussed and several conclusions can be summarized. Firstly, the significant improvement in fan bypass mass flow rate is achieved by jet mixing enhanced configuration at high back pressure operating point. Secondly, the performance is not degraded at low back pressure operating situation, but the total pressure loss is decreased at high back pressure operating point. Finally, the characteristic length of stream-wise vortex is the key to improve mixing performance, and the optimization of lobed mixer is available to match further structural requirement of adjust configuration.