The use of air-coupled ultrasonic transducers and the air medium presents issues with impedance mismatching, which can significantly reduce electro-acoustic conversion efficiency. To address this problem, this article introduces a novel acoustic matching layer made of hollow phenolic resin microspheres embedded in an epoxy resin matrix. The acoustic characteristics of this matching layer were thoroughly tested and analyzed. The test results indicate that the hollow phenolic resin microsphere matching layer demonstrates lower sound velocity and higher insertion loss compared to the hollow glass microsphere matching layer. Building upon these findings, an air-coupled ultrasonic transducer was developed. Two matched transducers were subjected to testing, and both the time-domain and frequency-domain characteristics of the received signals were analyzed, and compared their performance with the hollow glass microsphere matched layer transducers. The results revealed that compared with the hollow glass microsphere matching layer, the hollow phenolic resin microsphere matching layer can reduce the in-band undulation of the transducer, expand the -6 dB bandwidth of the transducer by more than 2 times, and reduce the tailing of the received signal in the time domain.