Abstract: The interferometer direction-finding system performs azimuth calculation based on phase difference. The miscalculation of solving ambiguity is inevitable when solving a single signal. To solve this problem, a method for judging the miscalculation in solving ambiguity of line array interferometer is proposed in this paper. For each baseline in the line array interferometer, the difference between the measurement value and the calculated value, corresponding to the baseline is calculated and normalized after obtaining the calculated phase difference value. The normalized phase difference errors corresponding to all baselines are accumulated and compared with the threshold value to determine whether there is a high error probability of sovling ambiguity of current signal. A drawer-ball-picking model is established based on the array configuration of the interferometer direction-finding system to calculate the probability distribution of the normalized phase difference errors. The selected threshold value is consistent with the principle of small probability event. This algorithm has a small computational load and is suitable for real-time calculation. This method can provide a basis for the subsequent data processing and improve the accuracy of direction-finding system. The simulation verification shows that the method showcases high judgment accuracy and prominent effect.