The invention belongs to the field of chemical industry, and particularly relates to a method for preparing methanol and coproducing natural gas from coke oven gas and coal gas. The method comprises the following steps: coke oven gas is subjected to desulfurization and impurity removal and mixed with treated coal gas, and is compressed to methanol main synthesis pressure and mixed with circulation gas of a methanol main synthesis system; the gas mixture enters the main synthesis system to synthesize methanol; the methanol generated by the main synthesis system is separated by a separator, subjected to flash evaporation in a flash evaporation tank and sent to a methanol rectification system; most of the gas after separation methanol is sent to a main synthesis circulation compressor to be circulated, and the rest gas is discharged out of the main methanol synthesis system as purge gas; the discharged purge gas and small synthesis system circulation gas are mixed to enter a small synthesis system; and the methanol is prepared by a purge gas technique. The irrational hydrogen-carbon ratio in the coke oven gas in the methanol and natural gas coproduction process is regulated by utilizing the coal gas provided by the coal gas making plant, thereby achieving the optimal hydrogen and carbon utilization; and the rich hydrogen and carbon contained in the methanol purged gas are reutilized and subjected to methanation to obtain the natural gas product.