<p>With the increasingly stringent control of particulate number (PN) limits in vehicle emission regulations, the limitations of traditional smoke density detection methods in diagnosing diesel particulate filter (DPF) failure and in-use vehicle supervision during China’s Phase VI period have become increasingly prominent. To address the current issues of portable PN detection devices that rely on complex dilution systems, have a large size, and face difficulties in meeting on-site rapid detection needs, this paper proposes a development scheme for a portable PN monitor based on an integrated design. By integrating core modules such as high-temperature tailpipe heating sampling, catalytic removal of volatile organic compounds, efficient counter-charge, and particle charge measurement, the device achieves direct measurement of high-concentration particulate matter without external dilution, significantly reducing the size of the device and improving the detection efficiency. Experimental validation demonstrated that the device exhibited a high consistency with Horiba OBS-ONE regulatory equipment in monitoring the trends in PN changes, peak positions, and heights, with a correlation coefficient of 91.5%. Comparative experiments among our newly developed PN monitors further indicated that the correlation coefficient of the measurements from three devices exceeded 99.9%, with absolute errors strictly controlled within 7%. Regarding DPF performance evaluation, the device could accurately capture the PN emission characteristics under DPF failure conditions. The average PN peak value was 1.5 × 10⁵&#xa0;#/cm³ under normal operating conditions, and it abruptly increased to 2.3 × 10⁷&#xa0;#/cm³ under failure conditions, with a difference of two orders of magnitude, visually quantifying the degradation of the DPF particulate trapping capability.</p>