Abstract: In order to obtain accurate and reliable data, system errors shall be controlled to an allowable limit. The errors in an industrial computer-based telemetery system are created mainly in the causes of systematic sampling, coding and signal transmission. Specific error causes are analysed respectively. Based on the theory, of error, measurement errors are classified into three categories: systematic error, random error and extensive error, and the data precision is determined in the following procedure: ① classify the category of the errors; ② decide whether systematic or extensive errors exist in the data measured; and ③ reject the abnormal data (extensive error), if any. Because computers are powerful in data processing, computer-based telemetery system can be greatly improved in terms of its precision provided sensors are duly selected and signals correctly acquired.