Abstract: The angular momentum budget equation in a moving coordinate system is given and the diagnostic analysis of angular momentum budget has been calculated for a monsoon depression over the India region on August 6-11,1979.The main results are as follows:(1) The time change rate of angular momentum is positive during the development of the depression and negative during its decay.(2) The lateral transports are the main source of the angular momentum,while the increase or the decrease of both the eastwind in the upper troposphere and the westwind in the lower level are the important factors affecting the transports.(3) When asymmetry exists in the pressure field,the pressure torque near the lateral boundaries is another important source of the angular momentum.(4) The friction torque is a main angular momentum sink.Thus it comes out that the lateral transport and the pressure torque near the boundaries are of most importance for the development and the maintenace of monsoon perturbations over the India region.