Plane heat conduction problems in functionally graded orthotropic temperature dependent materials are studied theoretically.The material properties such as specific heat c,density,thermal conductivities in x and y directions,respectively are assumed to be functions of temperature T and position (x,y).Introducing mapping function for temperature,the governing equation for mapped temperature 9 can be reduced to the governing equation without temperature dependent material properties.The steady state heat conduction problem in the functionally graded orthotropic plate (FGOP) with temperature dependent material properties is analyzed theoretically,when material properties are expressed by arbitrary functions of x and T such as λx =λx (x) g(T),λy =λy (x)g(T).