提出一種非定值相移量的單步相移同軸數字全息算法。對CCD面上的干涉光強進行了分析，用圖像相減法算出CCD面上不能確定相位正負的物光波，再記錄一幀有相移的干涉光強，來確定相位的正負。其特點是有相移的這一幀干涉光強沒有參與物光場大小的運算，只是用于相位符號的判斷。該算法對相移誤差不敏感。This paper describes an algorithm of numerical reconstruction for coaxial digital holography by means of a single phase-shift. In this algorithm, the intensity of the reference wave, the intensity of the object wave and their interference intensity are recorded, respectively, and the object wave is calculated from these three intensity frames, but the object phase is ambiguous. Then a phase-shift frame corrects the object phase. Compared with the other single phase-shift algorithm, the phase-shift frame in this algorithm is not joins in the calculations of the object wave, but makes it without ambiguity. So, the algorithm is not sensitive to the phase-shifted error.