Ultrasonic CT has been applied to thermal environmental measurements as a nonintrusive method. This research tries to develop a new ultrasonic CT reconstruction method to deal with the problem of insufficient projection data due to limited projection angle. The new CT reconstruction algorithm is based on inverse matrix transformation, which differs from the conventional CT reconstruction, known as FBP (Filtered Back Projection) with SL Filter. The current paper, describes three iterative CT reconstruction algorithms. Computer simulations were conducted to verify these algorithms, and the reconstruction results were compared. An experiment on 3 D temperature distribution measurement was carried out to validate the proposed algorithms. From the simulation and experimental results, normalized CGM (Conjugate Gradient Method), which takes account of regularized least squares, was Suggested to be the optimum iterative method for CT reconstruction under the condition of limited projection angle.