In recent years, microplastic pollution has attracted increasing attention from the public and scientific researchers. Microplastics have been reported to be widely distributed in water, soil and the atmosphere, and they may undergo aging process via physical, chemical or biological effects. At present, most of the researches on the aging of microplastics are carried out in aquatic environments. Meanwhile, the aging of microplastics were mainly characterized by off-line technology, which can only provide information on the structural changes before and after the aging treatment while the accurate interface reaction process is still unclear. Therefore, it is urgent to develop on-line monitoring technology for studying the aging process of microplastics and investigate their aging process in non-aqueous environment. One of the purposes of researching the properties of pollutants is to provide theoretical basis for studying its environmental impact. Therefore, in this study, the environmental process of polyvinyl chloride (PVC) agricultural mulch film entering the soil after aging in the air was chosen, and in-situ micro-Fourier transform infrared spectroscopy for single microplastic particle was developed, revealing the photochemical conversion process at molecular level. At the same time, the impact of photo-aged PVC microplastics on soil microbial communities was also investigated.