The digital pulse width modulator is one of the core modules in the digital switching power supply, its linearity is an important criterion to measure the digital pulse width modulator，and，of course，is also a major problem. In order to improve the linearity of the digital pulse width modulator, the paper proposes a calibration function of hybrid structure based on the times of capacitor charge and discharge, and discusses the working mechanism of the hybrid structure in detail. When system clock is 32 MHz, the digital pulse width modulator is realized that switching frequency is 1 MHz and resolution ratio is 10bits. The design for each module circuit is based on SMIC 180 nm technology to do postsimulation, compared to linearity of hybrid digital pulse width modulator based on counter and the delay line structure. The results show that the linearity based on capacitor charge and discharge with the digital pulse width modulator with calibration function is improved, and DNL is 0.125 LSB.