In this paper, the picosecond ultrasonic metal film thickness measurement based on asynchronous optical sampling with dual-comb is carried out to address the problems of the traditional picosecond ultrasonic technology based on mechanical delay lines, such as limited range and slow measurement speed. Based on two passively mode-locked ytterbium-doped fiber lasers working at 1030 nm waveband, a dual-comb picosecond ultrasonic measurement system is constructed. Based on asynchronous optical sampling, a time delay of 4 ns is generated, which is equivalent to a 0.6 m long mechanical delay line. Thickness measurement experiments are carried out on Au films with thickness of 43.67?165.33 nm, and the ultrasonic flight time is extracted by combining Gaussian filtering and multimodal Gaussian fitting to obtain a measurement resolution of ~2 nm. This device has potential application value for improving the film thickness detection process in chip, semiconductor, and micro-nano manufacturing.