Abstract: Utilizing meter-wave multiple input multiple output (MIMO) radar for the height measurement of low- altitude targets can significantly improve the accuracy of height measurement. However, the amount of data calculation in this process will increase substantially. To address this issue, this paper proposes two height measurement methods for low-altitude targets based on the maximum likelihood algorithm from the perspectives of dimensionality reduction preprocessing in the data domain and the beam domain respectively. These methods can effectively reduce the algorithm complexity while maintaining the accuracy, which is more conducive to practical engineering applications. The simulation experiments verify the effectiveness and correctness of the methods proposed in this paper.