Pseudomonas aeruginosa is a common opportunistic pathogen in clinics. The species-specific ecfX gene of Pseudomonas aeruginosa has high specificity. In this experiment, we are intended to develop a new method for the detection of Pseudomonas aeruginosa based on magnetic enrichment and nested PCR, and the specific ecfX gene of Pseudomonas aeruginosa was used as the detection object. The genomic DNA of Pseudomonas aeruginosa was extracted using amino-modified magnetic nanoparticles (MNPs). The ecfX gene was amplified by nested PCR and the product of PCR was detected by agarose gel electrophoresis. The results showed that the optimal annealing temperature was 64 degrees C and 62 degrees C respectively in the first and the second rounds of PCR. The lowest concentration of Pseudomonas aeruginosa that could be detected was 10 cfu/mL. The method provides a reliable, timely and accurate technology for early detection of Pseudomonas aeruginosa. Furthermore, the method can shorten the procedure and time from DNA extraction to detection, which made automation more convenient.