Random mutation is an important tool to elucidate the relationship between protein structure and function and to improve protein properties. The random mutation kit is based on error-prone PCR, which takes advantage of the fact that Taq DNA polymerase does not have a 3 '→5' collation function to introduce random mutation codon into the target gene in a specific reaction buffer system. The amplified products with random mutations were digested by double enzymes, linked to expression vectors to construct libraries, and then transformed into expression hosts for protein activity screening. If a mutation reaction fails to produce satisfactory results, a sequential error-prone PCR strategy can be used, in which a useful mutant gene amplified by one PCR is used as a template for the next PCR amplification, and random mutagenesis is repeatedly performed. So that each acquired mutation accumulates to produce a more meaningful mutation. This kit contains three components: optimized 2 x Mut Random System, Mut Enhancer and ddH2O. When used, it only needs to add an appropriate amount of DNA plate and two synthetic amplification primers, and make up the volume with water to perform the amplification reaction. Greatly reduce the chances of error and contamination caused by multiple samples. The 2 x Mut Random System contains optimized concentrations of Taq DNA polymerase, dNTPs, reaction buffers, and stabilizers to maximize the ability to overcome common error-prone PCR techniques. Due to the preference of Taq DNA polymerase itself, it has the disadvantage of being dominated by GC mutations, and a relatively balanced mutant spectrum is obtained. The base mutation rate can be controlled by adding Mut Enhancer, adjusting the amount of template DNA and changing the number of PCR amplification cycles.