Abstract: Disclosed is a process for preparation of biodegradable resin. The process comprises dehydrating a starch in a dehydrating kettle to a moisture less than 0.5%; finely granulating the dehydrated starch slurry to an average granule size below 10 &mgr;m; centrifuging the starch slurry to obtain a filter cake; adding to the centrifuged starch 0.5-5 wt % of a coupling agent and 0.5-7.5 wt % of a lubricant, based on the weight of dehydrated starch for modification; feeding the modified starch, 25-80 wt % of a thermoplastic resin, 1-10 wt % of a plasticizing agent, 0.5-7.5 wt % of a lubricant and 1-15 wt % of a degradation promoter, based on the weight of dehydrated starch, into a mixer and mixing them for 10-30 minutes under stirring, and then discharging them; extrusion-pelletizing the discharged material via a twin-screw extruder, the screws of which have length to diameter ratio of 40-48:1 and are of degassing function, at a temperature of 100-290° C.