A series of novel copolymers poly (AOBDA-co-DNMMA)s containing 2-Allyloxy-N-benzyl- idene dodecylamine (AOBDA) and 1.4-dioxaspiro[4.4] nonane-2-methyl methacrylate (DNMMA) were synthesized. The copolymers could form stable condensed monolayer at air/water interface and be transformed onto solid substrates successively. Positive-tone patterns with the resolution of 0.75 μm of the copolymers Langmuir-Blodgett (LB) films with 40 layers were obtained by deep UV irradiation, followed by developing in acetone. The etched gold patterns with resolution of 0.75 μm were also obtained, showing that the copolymer has enough resistance to wet etching suitable for fabricating photomask. The mechanism of photolysis was also investigated by UV, IR and GPC.