NOVELTY - Marsh gas biological purification and recycling of waste resources, involves (a) performing anaerobic fermentation of substrate mixture to produce biogas, (b) diluting fermentation residual biogas slurry with water and then passing into photobioreactor as medium of algae, (c) providing continuous light to the bottom of the reactor, and obtaining high quality methane, (d) using the algae that reached lag phase as inoculum for next culturing process, and (e) using anaerobic fermentation residue/compost as organic fertilizer to farmland to promote the growth of crops.    USE - The method is useful for marsh gas biological purification and recycling of waste resources, and producing high quality biogas methane used as chemical raw materials or fuel to generate electricity. The anaerobic fermentation residue/compost is useful as organic fertilizer to farmland to promote the growth of crops (all claimed).    ADVANTAGE - The method produces high quality biogas methane, provides zero emission of wastes, improves methane production from 30-40% to 90%, is economical, and recycles nutrient materials e.g. carbon, nitrogen and phosphorus. When the biogas methane is used as fuel to generate electricity, the power generation process collect the carbon dioxide produced into the photobioreactor, and use as carbon source of algae growth.    DETAILED DESCRIPTION - Method for marsh gas biological purification and recycling of waste resources, involves (a) performing anaerobic fermentation of substrate mixture, placed in anaerobic fermentation tank at 30-35 degrees C to produce biogas, where the substrate mixture comprises carbon substrate and nitrogen in a ratio (2( gamma 30):1), and pH of the substrate mixture is 6.5-7.5, (b) after fermentation, diluting residual biogas slurry with water to 20-40% of the original anaerobic fermentation slurry concentration, then passing into photobioreactor as medium of algae, where the photobioreactor uses sunlight as light source, the temperature of the photobioreactor is controlled to be 25 degrees C in the photobioreactor medium at pH 6.5-7.5, and the photobioreactor culture liquid depth less than 3 %mass, (c) providing continuous light to the bottom of the reactor, and obtaining high quality methane, (d) using the algae that reached lag phase as inoculum for next culturing process, and (e) using anaerobic fermentation residue/compost as organic fertilizer to farmland to promote the growth of crops, where the anaerobic fermentation residue/compost is optionally mixed with residual straw after crop harvest and then used.