Helical microrobots are envisioned for biomedical applications due to their capability of performing complex maneuvers required for a variety of on-demand tasks in biofluidic environments. Understanding the hydrodynamic interactions between helical microrobots and the surrounding fluid is crucial for their structural design,as well as the optimization of swimming dynamics and stability. In this letter, a high-order immersed boundary-lattice Boltzmann method (IB-LBM) is established for the investigation of the hydrodynamics of helical microrobots at low-Reynolds-numbers. In the proposed model, a method for positioning Lagrangian points on the helical microstructures is proposed and validated. For the implementation of IB-LBM, an approach for calculating the volume fraction is presented for distinguishing the helical body and fluid domains. The drag predictions obtained from the proposed model agree well with the laboratory measurements. The proposed IB-LBM method provides an effective tool for a comprehensive investigation of the hydrodynamic interaction between helical microrobots and the surrounding fluid.