This paper provide a proven case of “Warm Yang and Induce Diuresis” on differentiating and treating thymoma with large pericardial effusion and pleural effusion. It is believed that pericardial effusion is due to phlegmatic hygrosis and weakness of vital qi, so strengthening spleen and warm yang is the main therapy to strengthen body resistance, and purgation and promoting qi and removing blood stasis is the main therapy to eliminating the pathogenic factor. It is important to combine strengthening body resistance with eliminating the pathogenic factor and it is necessary to adopt the treatment both manifestation and root cause.