Presented is a kind of algorithm similar to amplitude demodulation for sonar array DOA (direction of arrival) for the purpose of simple algorithm, low processing requirement and low cost. According to the fixity of delay between units and the character of trigonometric function, the formula of DOA is got by deduction in the algorithm. Simulation results show that when the interval between units is quarter of wavelength, the precision is less than 0.3deg when SNR is 10dB and DOA is 5deg~-85deg the precision is less than 0.5deg when SNR is 0dB and DOA is 10deg~85deg and the precision is not more than 1deg when SNR is -10dB and DOA is 15deg~80deg. Simulation results also show that the precision can be less than 0.3deg by changing the proportion of units interval and wavelength, when SNR is between 0 dB~10 dB and DOA is 4deg~86deg.