The series of geomagnetic harmonic wave amplitude ratios are calculated in this paper,by using minute sampling data of 9 stations in Jiangsu from January 2009 to October 2016. The asynchronous changes of the long period and the short period of geomagnetic harmonic wave amplitude ratios are considered anomalous observed before earthquake. The geomagnetic harmonic wave amplitude ratio anomaly of Gaoyou station was found before the Gaoyou M4.9 earthquake,July 20,2012. And that of Yancheng station was found before the Sheyang M4.4 earthquake,October 20,2016. There are three anomaly features. The first one is asynchronous changes in the anomaly recovery period. The duration of anomaly is about 3 years and the amplitude of anomaly is between 0.02 and 0.17. The second,the amplitude of Y_ZHy is larger than Y_ZHx in two anomalies. The E-W direction is the principal compressive stress direction in the Gaoyou earthquake and the Sheyang earthquake. The direction of larger amplitude is considered to be consistent with the principal compressive stress direction.