The present invention is an ultra-thin low-pressure thermoplastic film and a preparation process thereof, and belongs to the technical field of thermoplastic films. The ultra-thin low-pressure thermoplastic film comprises the following components in percentage by weight: 45-60% of low-pressure polyethylene, 30-40% of special thermoplastic film polyethylene, 10-15% of masterbatch and auxiliary materials. The ultra-thin low-pressure thermoplastic film has low cost and good puncture resistance. The low-pressure polyethylene (with a dosage of 45-60%) is used as a main material to produce the ultra-thin low-pressure thermoplastic film, by use of the specific weight ratio of the low-pressure polyethylene and the special thermoplastic film polyethylene, the masterbatch and the auxiliary materials, the problem that the low-pressure polyethylene has poor flexibility and poor shrinkage and cannot be used as the main material for the production of the thermoplastic film can be solved, the low-pressure polyethylene is used as the main material to produce the ultra-thin low-pressure thermoplastic film, and knife is not easy to stick in the production process.