We synthesized some aromatic ester oligomers consisting of repeating units of oxy-1,4-phenylenecarbonyl group (ArESn, n=2∼4) as novel nonlinear optical (NLO) active chromophores and their methacrylate derivatives (ArESn-MA, n=2∼3). Some second-order NLO properties for poled polymer films of poly(methyl methacrylate) doped with 10 or 5wt%ArESn(ArESn/PMMA) andArESn-MAhomopolymers(poly(ArESn-MA))as well as copolymers with MMA(poly(ArESn-MA-co-MMA))were estimated by the second harmonic generation (SHG) measurement using Nd-YAG laser as light source. Comparison of thed33value at the chromophore molar concentration (d33(M)) forArESn/PMMAfilms indicated that thed33(M) value ofArESnincreases with increase in n andArESnwith n more than 3 reveal higherd33(M) value than that ofpNA, in addition, everyArESnhas cutoff wavelength (λco) of about 300nm, which is much snorter than the case ofpNA (λco=ca. 450nm). Moreover,poly(ArESn-MA)films exhibited much largerd33values than those ofArESn/PMMAfilms since the formers contain the chromophores in high concentration, however, when the comparison is made by using thed33(M) value the values become less than 1/2 of those in the cases ofArESn/PMMAfilms. This might be caused by a strong interaction acting among the chromophore side chains. Copolymerization ofArESn-MAwith MMA which is capable of relieving the interaction improved the chromophore orientation considerably.