This paper presents a novel asymmetric microactuator based on photo-thermal expansion. It has an asymmetric structure consisting of two thin expansion arms with different widths. When a beam of infrared laser irradiates the arms，the different increases in temperature and photo-thermal expansion controlled by the different rates of specific surface area causes a magnified lateral deflection. In the paper，the thermodynamic model is introduced，and the computing formula of lateral deflection is given. A prototype microactuator of 750μm length has been manufactured by using the excimer laser micromaching system Optec Promaster with an infrared laser diode (998nm) as the external power source to activate the microactuator. Then we carried out feasibility experiments by using a monitored control system made by our laboratory，and measured the relationship between the lateral deflection and laser power. The experiment results demonstrate that the deflection of the microactuator reached 258μm at 16mW infrared laser power. The photo-thermal microactuator has the advantages of simple structure，adjustable deflection，no electromagnetic interference，easy integrating and remote controlling. It will be quite useful for applications in the fields of micro/nano-technology and micro-electro-mechanical systems (MEMS).