To address the limitations of conventional linear array beamformers, such as their single functionality and poor signal-to-noise ratio (SNR) gain, a controllable beamforming method for rectangular arrays was proposed. The method was based on the Kronecker product principle, where a rectangular array was decomposed into two virtual linear sub-arrays for analysis. The steering vector of the rectangular array was represented as the Kronecker product of the steering vectors of the two virtual sub-arrays. A differential virtual sub-array with controllable nulls was then designed by utilizing the orthogonality between the beamforming filter and the steering vector. The second virtual sub-array was designed using a delay-sum beamformer (DS) and a superdirective beamformer (SD). The two virtual sub-arrays were then integrated to create a high-gain, null-controllable beamformer and a high-directivity, null-controllable beamformer based on a rectangular array. Simulation experiments analyzed the beam patterns, white noise gain (WNG), and directivity factor (DF) of the rectangular array and the two virtual linear sub-arrays. The results show that the proposed beamformer achieves controllable nulls and significantly improves the SNR gain compared to a single virtual sub-array. It is suggested that this approach be applied in scenarios where high-gain and high-directivity beamforming are required.