Abstract: In the coalbed methane fields in southern Sichuan, aiming at the problem of composite scale caused by ferric salt and coal slime in the wellbore, researches on anti-scaling technology combining laboratory experiments and field engineering were carried out. The method for evaluating indoor experiment was established, and the experiment dispersing coal powder particles and the experiment preventing coal slime from consolidation were completed with 3 kinds of organic phosphonic acids and 2 kinds of polymer agents. The influence of chemical agents on particle size distribution and Zeta potential was investigated by dynamic light scattering and surface Zeta potential testing, and reasons influencing the effects of chemical agents on the dispersion of coal particles and the consolidation prevention of coal slime were preliminarily analyzed. The research results show that the ethylenediamine tetramethylenephosphonic acid (EDTMPS) in the organic phosphonic acids is of good dispersibility, however, due to the influence of high ferric salts, the coal slime consolidation prevention ability of the EDTMPS is poor, which is not suitable for scaling prevention in this area. Nevertheless, polymer agents are more suitable for scaling prevention and control under such complex water quality. According to the characteristics of the agents, the combined process of dispersing consolidation prevention and periodic well cleaning was implemented in the field construction. The scaling rate of coalbed methane wells in the block has been significantly reduced since the program was launched 3 years ago, and the pump inspection period was extended to 1.3 to 3 times, achieving perfect application effect.