A laser technique of transient burning rate measurement of solid propellant has been investigated. A photocell detects a laser beam passing through the propellant strand, and the cross-section of the laser beam is regulated so that the laser energy varies linearly along the height of the strand. Using a photo-controlled depressurization system, it is desirable to set up the starting time of depressurization in advance, and the initial rate of depressurization can be easily reproduced. Experimental results show that: (1) for a short time after depressurization begins, the burning rate remains unchanged; (2) during the depressurization process, the burning rate, while continuously decreasing in magnitude, exhibits low frequency oscillations; (3) the amplitude and the frequency of the burning rate oscillations, referenced to a smooth rate-time curve, increases as the depressurization rate increases: (4) for a short time after depressurization, the transient burning rates is higher than the steady state burning rate at the corresponding pressure, and then the transient burning rates oscillate around the quasi-steady rate. The experimental dynamic burning rates are compared with those available by microwave and capacitance methods. The discrepancies in the three experimental results have been discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.