Abstract: The cement deep mixing (CDM) pile is a widely-used method for soft ground treatment in Huanghua Port region. However, construction quality problems easily occur. Based on the field inspection results of CDM in Huanghua Port region, two construction quality problems of CDM are systematically analyzed. In order to investigate the causes of construction quality problems, indoor mix proportion tests on three contents of cement under different test periods are conducted to exclude such factors as content of cement and soil texture. Through the comparison of difference between indoor mix proportion tests and field construction of CDM, the field construction technology is pointed out to be the main cause of quality problems. Finally, two effective construction technique improvements of cement deep mixing pile are proposed. The successful application of bidirectional mixing technique in the Huanghua Port region is introduced, and the relevant inspection data is provided for reference. In addition, a fan-shaped back-spraying stirring head is demonstrated to be an effective construction technique to solve the two above construction quality problems.