The invention discloses a system and process for raising the temperature of a methanolization-methanation catalyst by using a molecular sieve regeneration gas through the separate operation of a low pressure cylinder of synthetic turbine and a high pressure cylinder of synthetic turbine. The cost is saved, the pollution is reduced, and the catalyst poisoning is avoided. The technical scheme is as follows: a molecular sieve regeneration gas pipeline is transformed to be connected with a pipeline subjected to shift gas removal, pre-removal, hydrolyzing, purifying and decarbonization from the previous shift gas removal system inlet pipeline; when the temperature is raised, a decarbonization outlet valve is closed, and a methanolization-methanation temperature raising pipeline is stopped to be used, and is replaced with a molecular sieve regeneration gas pipeline. A 80m-long DN350 buffer pipeline between the decarbonization system outlet valve and a synthetic turbine inlet valve plays a buffer role, a valve in a direct communicating pipeline of the low pressure cylinder and the high pressure cylinder of the synthetic turbine is closed, and the low pressure cylinder and the high pressure cylinder of the synthetic turbine are driven by a steam turbine to separately operate.