In this paper, we present the application of automatic test equipment (ATE) in digital circuit boards design. Test validation for spare part boards design using ATE hardware and LASAR software was discussed, and examples were also given. The results showed that the simulating technology was an efficient way for circuitry design and validation, and the use of ATE as the general purpose test and validation platform is feasible. The major requirements for spare part boards design are to satisfy technical parameters and performances requirements and, to build running environment and test environment under the laboratory condition. The primary purpose is to verify that whether the functions and performances of spare part circuit boards are identical to the original circuit board under the same stimulating and operating condition, therefore to ensure the design requirements. Test program sets (TPS) running on ATE are developed on the platform of LASAR simulation software. Since LASAR can be used to simulate the performances of digital circuits, it can also be used in digital circuits design validation, and the development of test program sets.The key technical approach is that, the original circuit board must have passed GO/NOGO TEST [4] on the Spectrum 9023/50 ATE by running corresponding TPS; then the spare part board is tested under the same testing condition; finally, by comparing the test results, the designer is able to find out the problems occurred, analyze the causes and modify designs accordingly.First of all, we describe the approach of designing spare part circuit boards. Then we introduce TPS development work flow on LASAR simulation platform. Finally we will give the practical cases of test application and summarization of the spare part design at the end of this paper.