The dynamic properties of optothermal microactuator (OTMA) are theroretically and experimentally reported under pulsed laser irradiation.A dynamic model for describing optothermal temperature rise a nd optothermal expansion of the expansion arm is established.The formulas of dynam ic expansion and its amplitude are also derived,based on which the relationships among the expansion,expansio n amplitude and the laser pulse frequency are obtained through Matlab simulations.An asymmetric optothermal mic roactuator (A-OTMA) with length of 700μm is designed and microfabricated.Expe riments are carried out under pulsed laser with power of 2mW and frequency of 2－18Hz.The dynamic actuating of the A-OTMA is monitored by microscopic imaging system and is further analyzed using motion analysis software.The experimental results show t hat the A-OTMA can periodically deflect with the same frequency of laser pulse,and both of the max imum deflection and deflection amplitude decrease as the frequency increases,matching with the trends of theor etical curves quite well.It is also proved that the A-OTMA is capable of acquiring maximum deflection amplitude of 14.9μm (at 2Hz) and maximum response frequency up to 18Hz.This work can provide technical found ation for practical applications of optothermal microactuator in the fields of micro opto-electro-mechanical sy stem (MOEMS) and micro/nano-technology.