Abstract: An analytical model for laser –induced heating, heat conduction and thermal stress crack of a brittle thin target is proposed. The analytical expressions are induced for the temperature increment and thermal stress that varies with time, which can be described as h I0b2/Kh and a Eh I0b2/Kh , respectively, while their space –time distributions being expressed as a infinite series. The threshold laser parameters for thermal stress crack of K9 glass and MgF2 ploycrystal targets predicted by this model are in agreement with those obtained experimentally.