This paper presents a scalable parallel ultrafast optical random bit generation scheme based on a single chaotic microcomb. The method leverages the chaotic modulation instability (MI) in a micro-ring resonator (MRR) to generate hundreds of independent and unbiased random bit streams simultaneously. A proof-of-concept experiment demonstrates that using this method, random bit streams exceeding 2 terabit per second can be generated with only 7 comb lines, and the bit rate can be further enhanced by increasing the number of comb lines. The approach offers a chip-scale solution for secure communication and high-performance computation, providing superhigh speed and large scalability. The chaotic microcomb is generated using a CMOS-compatible, high-index, doped silica-glass MRR, which is simple to fabricate and package, making it suitable for on-chip implementation. The experimental results show that the generated random bit streams pass all NIST tests, confirming their statistical randomness. This work significantly advances the field of physical random bit generation by achieving ultrafast and scalable rates.This paper presents a scalable parallel ultrafast optical random bit generation scheme based on a single chaotic microcomb. The method leverages the chaotic modulation instability (MI) in a micro-ring resonator (MRR) to generate hundreds of independent and unbiased random bit streams simultaneously. A proof-of-concept experiment demonstrates that using this method, random bit streams exceeding 2 terabit per second can be generated with only 7 comb lines, and the bit rate can be further enhanced by increasing the number of comb lines. The approach offers a chip-scale solution for secure communication and high-performance computation, providing superhigh speed and large scalability. The chaotic microcomb is generated using a CMOS-compatible, high-index, doped silica-glass MRR, which is simple to fabricate and package, making it suitable for on-chip implementation. The experimental results show that the generated random bit streams pass all NIST tests, confirming their statistical randomness. This work significantly advances the field of physical random bit generation by achieving ultrafast and scalable rates.