Multi-channel Analyzer (MCA) is one of very essential equipment in nuclear physics and nuclear engineering for the measurement of ionization radiation. Generally, an MCA system consists of radiation detector, amplifier system, ADC circuit, and MCD connected with computer for data processing. Among them, ADC is a functional electronic block, which plays an important role for converting analog to digital signals. Corresponding to the domestic needs in development of nuclear instruments, this work presents a design and construction of an ADC8K module with successive approximation method. Some experimental results are as follows: Differential non-linearity (DNL%) = 1.42, Integral non-linearity (INL% = 0.58), and χ² = 8.109 proved that mentioned system can be used with considerable reliability in practical nuclear engineering.