A few common periods in the series of residual latitude (O-C) of four stations in China have been found by means of maximum entropy power spectrum, periodogram and least square fit methods.

• 本文用我国四个台站的剩余纬度(O-C)序列,用最大熵功率谱、周期图和最小二乘拟合的方法找出了四个序列中共同的周期。