The dot product function is a first-level basic function in the BLAS library, which is widely called by scientific calculations and other fields. As the floating-point calculation introduces rounding errors, the double-precision dot product is unable to meet the accuracy requirements in some application fields, and thus high-precision algorithms are needed to achieve more accurate and reliable calculations. In this study, on the basis of the existing BLAS library, the interface of the high-precision dot product function is added to meet the high-precision requirements of applications on the domestic SW1621 platform. At the same time, the high-precision dot product algorithm uses such optimization strategies as loop expansion, visit-memory optimization, and instruction rearrangement to realize assembly-level manual optimization. The experimental results indicate that the high-precision dot product algorithm has the accuracy approximately twice that of the double-precision dot product, which effectively improves the precision of the original algorithm. On this basis, the average performance speedup of the high-precision dot product function reaches 1.61 after optimization.