Abstract: To study the relationship between the parameters of the ultrasonic coda wave signal and the load grades of concrete structure, an ultrasonic coda wave test of the T-beam under three-point bending load was designed and implemented. The ultrasonic coda wave test data of the T-beam under 22 load levels were collected by using Taylor expansion formula, and the first five signal components of the ultrasonic coda wave test data were extracted and analyzed. On a basis of it, the higher-order signal components were successively eliminated, the first signal components of the ultrasonic coda wave test data were retained, and the first-order signal parameters were extracted from it. The relationship curve between the first-order signal parameters of the ultrasonic coda wave test data and the load levels of the T-beam was established. Results show that there is an approximate linear relationship between the first-order signal parameters of the T-beam and the load levels, and the fitting goodness of the linear is better than 0.99.