To develop tunable trtansversely excited atmospheric (TEA) CO2 laser used in differential absorption lidar (DIAL) system, the kinetic characteristic of a TEA CO2 laser is investigated, base on the theory of six-temperature model rate equation. The output characteristic of the laser is calculated. A rapidly tuned TEA CO2 laser at high repetition frequency is manufactured by the result of calculation. With the method of a resonant reflecting mirror scanning a fixed grating, the rapidly tuned TEA CO2 laser output is realized. The pulse energy of spectral lines such as 10P(42)～10P(48) in fundamental-transverse mode is over 100 mJ at a repetition rate of 100 Hz, and the pulse width is no more than 100 ns. The far-field divergence angles of 10P(46) spectral line are 2.41 mrad (horizontal) and 2.27mrad (vertical), namely, 1.6 times of diffraction limitation. The laser can be tuned between two different rotational lines spanning the wavelength range within 10 ms.