<p>The bound states in the continuum (BICs) of the photonic crystal (PhC) formed by period rectangular nanopillar arrays are demonstrated. By varying the structural parameters of rectangular nanopillar array, it is proved that the angle of incident light, the surrounding dielectric, and the number of nanopillars in a period can regulate BICs effectively. With the change of the number of nanopillar and structural parameters in period, the locations of both at-Γ BICs and off-Γ BICs change and the ultrahigh-quality factor (<i>Q</i>-factor) of BICs are obtained with a value more than 10⁶, which means the light has been completely confined in this nanopillar array structure. The BIC modes of this structure are related to the structural parameters of the metasurface, and the BIC has a high sensitivity to the change of the refractive index of the surrounding medium. This advantage of high sensitivity is conducive to the design of new photonic devices based on BIC, such as lasers, filters, and sensors.</p>