Aiming at the general problems of wideband array radar, i. e. , beam pointing drift and main lobe width jitter caused by aperture fill, we deduced the causes through basic signal theory and array processing technology by using chirp signal as the transmitted signal, and analyzed their influence on beam-pointing and beam-width of the radars under different relative bandwidth. According to the theoretical analysis, a stable method for wideband beam forming was proposed, combining fine adjusting technique of array element carrier frequency with time-domain resambling. Theoretical analysis and simulation results demonstrate that with this method, the beam pointing and the main lobe width of the beam of wideband array radars can keep stable within a pulse duration. Meanwhile, with characteristics of simple structure, small calculating amount and fast speed, the method is applicable to real-time systems and convenient for engineering implementation.