Different pre-treatment methods on the extraction of sodium alginate were studied and Glutaraldehyde was used as the optimal solution instead of formaldehyde.The results showed that 2%(v/v) glutaraldehyde was superior to formaldehyde as treatment solution.The optimum conditions of extraction were obtained as follows: ultrasonic power 50w,microwave power 500w,extraction for 60s,solid to liquid ratio of 1∶ 20,extraction 2 times.Compared with other extraction methods,the ultrasonic-microwave synergistic extraction was a better method for sodium alginate extraction with less time and higher extraction rate.This is a better method for extracting sodium alginate.