The emerging Orthogonal Time Frequency Space (OTFS) technique can achieve stable communication in high-speed mobile scenarios, which combining with multiple-input multiple-output (MIMO) can improve the spectrum and energy efficiency of wireless communication systems. To achieve potential performance gains of OTFS-MIMO systems, this paper considers the precoding design for wideband OTFS-MIMO systems with beam squint effect. We propose a novel precoding structure with compensation modules for eliminating the influence of beam squint and further improving the achievable rate. The simulation results prove that the achievable rate of the wideband OTFS-MIMO system with beam squint has been significantly improved under our proposed scheme.