Magnetoelectric multiferroic composites, which combine ferroelectric and ferromagnetic phases, are pivotal for next-generation electronic devices. Conventional design strategies prioritize ferroelectric materials with large spontaneous polarization to achieve strong magnetoelectric coupling. Here, we propose a paradigm-shifting approach that instead utilizes a material’s high strain sensitivity of polarization. The quantum paraelectric SrTiO3 is discovered as an ideal ferroelectric component due to its exceptionally high polarization response to strain, far exceeding that of classical ferroelectrics like BaTiO3 or PbTiO3. To demonstrate this concept, the desired SrTiO3-NiO nanocomposite films featuring ordered nanopillar array and atomically sharp vertical interfaces were fabricated. This nanostructure maximizes the interfacial contact area and ensures highly efficient strain transfer. The resulting composite exhibits a giant direct magnetoelectric coupling coefficient of 3200 mV/(cm·Oe) at room temperature, demonstrating a remarkably strong macroscopic magnetoelectric response compared with conventional 1-3 composite oxide multiferroic systems. Through a combination of atomic-resolution scanning transmission electron microscopy and first-principles calculations, we reveal the outstanding performance originates from the unique strain-sensitive polarization of SrTiO3, which can effectively trigger substantial polarization variations via magnetic field-induced strain transfer across coherent interface. This work redefines the design principle for high-performance magnetoelectric composites by emphasizing strain sensitivity over large polarization, opening a new pathway for developing ultra-sensitive sensors and multi-state, low-power memory devices.