The kit has optimized a series of transcription reaction systems for different templates and different nucleotide types, and users can efficiently obtain a large number of RNA products from DNA through this product. The kit uses RNA polymerase that recognizes T7 promoter, takes plasmid or PCR product containing T7 promoter sequence as template, uses natural nucleotide or modified nucleotide as substrate, and can obtain high-yield single-stranded RNA through short in vitro transcription. At the same time, complete mRNA with hat structure can be transcribed by this kit by adding Cap0 or Cap1 and other hat structure or hat structure analogues to the substrate. This kit is recommended to use 20μL in vitro transcription system, input 1μg plasmid template or equivalent PCR product template, use natural or modified nucleotides, in vitro transcription yield of more than 200μg, through process design and optimization, can be used for the amplification of gram level RNA production. The RNA synthesized by transcription can be used to analyze the properties and structure of RNA. Single-stranded RNA without hat structure is easy to degrade, so we suggest downstream processing according to project requirements, and cyclic RNA should be processed downstream as soon as possible. Linear RNA can be capped by vaccinia virus capping system and dioxymethyltransferase. The use of cotranscription capped mRNA can be directly used in the study of mRNA function.