Droplet digital polymerase chain reaction (ddPCR) technology has found widespread applications in the ultrasensitive analysis of nucleic acids, where integrated ddPCR platforms with the capability of sample dispersion, followed by in situ amplification and data analysis, are highly expected. However, current integrated ddPCR platforms are usually limited by either difficultly mass-produced materials or lack of integrated control instruments, restricting their practical application. This paper proposes an integrated three-in-one ddPCR platform with high user-friendliness and practicability, which is composed of an easy-to-use chip and a matching control instrument. The chip was made of thermally resistant and easily mass-produced polycarbonate (PC) material, and the benchtop control instrument was designed to perform droplet generation, in situ amplification, and fluorescence reading. The droplet generation and in situ heating on the chip were well characterized. Finally, the performance of the platform was validated through the analysis of the EGFR L858R mutation in lung cancer. The proposed three-in-one ddPCR platform shows great practicability in ultrasensitive nucleic acid testing. By virtue of its sensitivity, practicability, and cost-effectiveness, the ddPCR can serve as a universal detection platform for monitoring nucleic acid in the fields of tumor diagnosis, pathogen detection, and prenatal diagnosis.