A new bunch current measurement system has been implemented in Hefei Light Source II (HLS II) recently. This system is based on the photodetector and synchrotron radiation. This paper presents the system structure and a waveform reconstruction algorithm. Through the dedicated equivalent-time sampling algorithm, the effective sampling rate is nearly 225 GS/s, which meets the needs. Then, the absolute value of the bunch current is calibrated by the DCCT. Those data processing program is supported by the LabVIEW. Preliminary test results in daily operation, single-bunch and "HLS" fill pattern modes show that the system is working reliability, providing a convenient and robust tool for the top-up mode operation in the future.