Eight new aliphatic symmetrical diphosphonium salts were synthesized by reacting ω,ω´-dibromoalkanes with triphenylphosphine or tributylphosphine using N,N-dimethyl acetamide as a solvent at 140~150°C for 16~20 h under a nitrogen atmosphere. Product characterization analyses and germicidal tests against saprophytic bacteria, sulfate reducing bacteria and iron bacteria were performed. Three compounds showed bactericidal effects, including 1,12-di(tributylphosphonium bromide) dodecane, which provided the best results of 98.0%, 96.4% and 99.8%, respectively., at a concentration of 20 mg/L against the saprophytic bacteria, sulfate reducing bacteria and iron bacteria. All of the compounds were tested under identical conditions, including the same effective dose and contact time.