A new technique base on femtosecond laser local field enhancement effect is proposed. Nanomachining of thin gold films was accomplished by coupling 800 nm femtosecond laser radiation with an atomic froce microscope Si3N4 tip in ambient air by the local field enhancement effect. Possible factors affecting this process are discussed like the speed of the fabrication and the laser fluence. At last we get the high spatial resolution of (～10 nm) (not possible with standard nanomachining techniques). The presented process provides an intriguing means for massive nanofabrication due to the flexibility in the substrate material selection and easy lithograph of complex pattern.