Polyamide (PA) composite membranes were prepared by interfacial polymerization with piperazine, m-phenylene diamine, and trimesoyl chloride as monomers and polysulfone ultrafiltration membranes as supports. Factors affecting the performances of the composite membranes by changing the characteristics of the PA active layers were studied. First, the monomer compositions were varied, and organic solvents (benzene and 1,2-dichloroethane) with better solubility for PA than hexane were used for the interfacial polymerization. As chemical additives capable of changing the property of the interface formed between water and organic phases, n-propanol and i-propanol were used, and phase-transfer catalysts such as triethyl benzyl ammonium bromide were used to improve the polymerization efficiency of the PA active layers. The characteristics of the PA composite membranes prepared, including their permeation properties and morphology, were carefully studied with various analytical methods, such as field emission scanning microscopy, atomic force microscopy, differential scanning calorimetry, and permeation testing.