As for the screen test requirement of control circuit hardware in servo system, analyses and determines the sampling error of the position feedback acquisition circuit for the typical value, in order to eliminate failure products in batch production. The position feedback acquisition circuit mainly consists of an operational amplifier follower,an A/D converter and voltage references modules. The sampling errors of the above three modules for 2.5 V are calculated respectively, combined with the error of test equipment, consequently the maximum sampling error of the hardware circuit is 25 LSB. Finally, the test error range is effective and accurate, the screen method can eliminate defective products in circuit boards delivery and avoid fault products into next section, that were illustrated by examples.