A novel current transducer based on rectangular array of magnetic sensors is proposed. It is a valid alternative to traditional current transformers in high power dc busbar systems for fusion applications. Since measured magnetic fields along rectangular closed integral path fluctuate violently, sum-average algorithm, which is most commonly used by circular arrangement sensor array, does not fulfill the accuracy requirement any more. Numerical quadrature algorithms of high orders are applied to improve rectangular array’s accuracy. The algorithm can be implemented by multilevel adder of analog circuit. Optimum dimension of rectangular array, error introduced by installing deviation and crosstalk interference are analyzed theoretically. The experimental results sufficiently verify the accuracy and reliability of the proposed transducer.