This study discusses hydrodynamic effects of horizontal spoilers fixed on submarine pipelines. Numerical calculations are conducted to investigate the influences of the spoiler on flow profile, vortex shedding frequency, drag coefficients and lift coefficients. The calculation results demonstrate that attached horizontal spoilers could change the wake flow and enhance the self-burial of the pipeline. Moreover, the vortex-inhibition effects of different sizes of spoiler are discussed. The length of horizontal spoilers between 1.0D~1.5D has the optimal effect. The results would be promising for the application to submarine pipelines.