Using a tethered balloon as a flight platform for a hyperspectral camera, a two-axis stable platform was designed to compensate the attitude change of the platform in the heading and pitching directions. The azimuth and pitch driving mechanisms of the stable platform were powered by a cable drive. The continuous driving torques of the azimuth and pitch axes were 93.6 N?m and 117 N?m, respectively, and the maximum rotational speeds of the shafts were 25 (°)/s and 20 (°)/s, respectively. The test results show that the transmission accuracy of the stable platform is 5 μrad, and the transmission error is less than 0.7%. The servo bandwidths of the azimuth and pitch axes are 15 Hz and 35 Hz, respectively. The root mean-squared (RMS) errors of the sinusoidal tracking accuracies of the azimuth and pitch axes are 0.0045 and 0.0043, respectively. An outfield flight test was performed with a 35-kg hyperspectral camera mounted on the stable platform pitching frame to conduct air-to-earth observations, and the gyro stability data of the flight test was monitored. The RMS stability accuracy of the azimuth axis (38.83 μrad) and the pitch axis (37.26 μrad) met the 50-μrad requirement of the hyperspectral camera.