The general solution of TEM00-thermo-insensitive cavity in the presence of several thermo-perturbation centers has been obtained by means of the transformation circle diagram. In this cavity the circles π in the places of thermo-perturbation centers are tangent successively; one of the circles π1 is tangent to the circle σ1 of the mirror R1 of the cavity; and the spot sizes of the fundamental mode determined by the circles π satisfy the requirement selecting fundamental mode by self-diaphragm. At the same time, the simple designing process and calculating formulas of such cavity, particularly a frequency doubled cavity, has been established according to this solution.