Polyethylene glycol perfluorononyl monoethers (C9F17–PEG-n) and diethers (C9F17 –PEG-n–C9F17) were prepared from polyethylene glycol (PEG-n) and perfluorononene (C9F18), the relations of surface performances to molecular of C9F17–PEG-n and C9F17–PEG-n –C9F17 were investigated. Their surface tensions(γ), critical micelle concentrations(CMC), cloud points, foaming characterisitics and emulsifiabilities were studied. C9F17–PEG-n–C9F17) is smaller minimum molecular area(Amin), greater saturated adsorption quantity (Γm), lower clued point, worse emulsifiability for toluene, but better surfactivities and greater foaming volume of their aqueous solutions than C9F17–PEG-n. For C9F17–PEG-n or C9F17–PEG-n–C9F17, Γm decline, Amin increase and the emulsifiability becomes better for toluene along with the increase of n; the CMC, γCMC and clued point of their aqueous solutions ascend, their foaming volumes increase and then decline and get the biggest value at n=1000.