Efficient massive MIMO detection for practical deployment,which is with spatially correlated channel and high-order modulation,is a challenging topic for the fifth generation mobile communication (5G).In this paper,we propose a lattice reduction aided expectation propagation (LRA-EP) algorithm for massive MIMO detection.LRA-EP applies expectation propagation in lattice reduced MIMO system to approach the distribution of lattice reduced constellation point by iterative refinement on its parameters (mean and covariance).The parameter refinement is based on the lattice reduced,well-conditioned MIMO channel.Numerical result shows that LRA-EP outperforms classic EP based MIMO detection (EPD) with 5～7dB in terms of required signalto-noise ratio (SNR) for 1％ packet error rate in spatially correlated channel for 256-QAM.We also show that LRA-EP has lower computation complexity than EPD.