High-speed optical amplitude modulation is important for optical communication systems and sensors. Moreover, nano-optical modulators are important for developing optical-communication-aided high-speed parallel-operation processors and micro-biomedical sensors for inside-blood-capillary examinations or microsurgery operations. In this paper, we have designed a plasmonic resonant tunable metasurface with barium titanate (BTO) as a nanoscale optical modulator with a high modulation index and high speed. The BTO operated well in the VIS and near-IR ranges, enabling tunable optical devices with zero dispersion and high speed. The results obtained by rigorous finite-element method simulations have shown that the hypothesized device has good potential for fast modulation in related applications, e.g., modulators in nano-optical systems, nano-optical switches and nanosensors.