A bipolar low pass filter with the adjustable bandwidth comprises a main filter unit, a secondary filter unit, a phase-frequency detector, a filter unit and a digital-analog converter unit. In the invention, an indirect regulating circuit is formed by a principal and subordinate structure of the main filter unit and the secondary filter unit to ensure the precision of the main filter unit, thus ensuring that the precision of the bandwidth of the whole low pass filter is guaranteed; the bandwidth can be adjusted by the digital-analog converter unit; the digital-analog converter unit is controlled by a number command signal of an external integrated circuit bus, thus controlling the bandwidth of the whole low pass filter, that is, the bandwidth of the low pass filter can be controlled by theexternal, which expands the applied range of the low pass filter circuit; the filter has high the precision of control frequency and easy circuit realization.