Degradable straw is produced by fermenting renewable resources such as corn, potato, crop orange stalk and so on, and further purifying and polymerizing high purity polylactic acid as raw material. The raw material of polylactic acid straw is crops, which are made by modern biological fermentation technology. Toxic gases such as nitride and sulfide will not be released during incineration. Under the condition of composting, it can be degraded into carbon dioxide and water by microbial action within half a year.