An RTP heating system and an RTP heating method, which can heat a photovoltaic-device intermediate product having a glass substrate, a Mo layer, and a light absorption layer in formation. The RTP heating system is composed of a chamber; a support member located in the chamber; a heating element mounted in the chamber for emitting infrared rays for heating; and a plurality of temperature sensors and a temperature control device for sensing and controlling thermal sources from the heating element and the support member. The infrared rays can be mostly reflected off the Mo layer to apply less direct heating to the glass substrate. Accordingly, the upper and lower surfaces of the photovoltaic-device intermediate product can be heated under different temperatures separately to prevent the glass substrate below the photovoltaic-device intermediate product from softening and deformation and to allow production of the light absorption layer on the Mo layer.