The invention discloses a microstrip ultra wide stop band low pass filter. The filter comprises a double-faced copper-coated microstrip plate with two surfaces, wherein an input end feeder, an output end feeder, uniformity impedance resonators which are opposite left and right, step impedance resonators which are opposite up and down and connecting wires are respectively made on the same surface of the double-faced copper-coated microstrip plate, a defected ground structure is made on the other surface of the double-faced copper-coated microstrip plate, the step impedance resonators which are opposite up and down are mutually connected and are arranged between the uniformity impedance resonators which are opposite left and right, the uniformity impedance resonators which are opposite left and right are respectively connected with the step impedance resonators which are opposite up and down by the respective corresponding connecting wire, and the input end feeder and the output end feeder are respectively connected with the corresponding uniformity impedance resonator. The microstrip ultra wide-stop band low pass filter has the advantages of simple and reliable structure, good selectivity, low loss, fast roll-off, small size, low cost, ultra wide stop band and the like.