The invention relates to a method for evaluating erosion rate of a sand control pipe and its special-purpose apparatus, which is characterized in that the on-site screen casings are used for processing to screen casing sheets for experiments. According to the invention, change of sand control pipe precision can be evaluated by a laser granularity analysis on sand from different periods of experiment process, erosion rate of the screen casing under specific reservoir condition and production condition can be evaluated according to the mass change of the screen casing sheet before and after the experiment, and finally the erosion rate and the usage life of the screen casing can be predicted. For solving the problems, a technical scheme is characterized in that the special-purpose apparatus is a whole set of fluid circulation apparatus, which comprises a circulation solution storage pot 1, a high pressure pump 2, a pressure gage 3, a flow monitor device 4, a safety exhaust valve 6, a pressure transducer 7, an enclosed autoclave body 8, an oil-sand separator 9, and a data acquisition system 10. According to the special-purpose apparatus, an erosion stand 14, a cleaning nozzle 22 and a sand washing nozzle 15 are arranged in the enclosed autoclave body 8.