With the social and economic development, there is growing demand in agricultural technique English. But there exist some obstacles in agricultural technique promotion. Some translators haven’t paid attention to their needs and education levels of target readers in agricultural promotion that proves to be obscure translation rather than simple farming method. This paper conducted an investigation on modal values based on Halliday’s systematic modality theory. Corpus quantitative research approach was used in the hope of gaining more insights into agriculture technique English. A comparative analysis was made between Brown Corpus and agricultural English Corpus(AEC) which contains 400 000 words, summarizing the differences in application of modal verbs across the two corpora. This study aimed to probe into modal values in practice of agricultural technique promotion texts in a way, which could be better understood by readers of target language. With the social and economic development, there is growing demand in agricultural technique promotion. Some translators have not paid attention to their needs and education levels of target readers in agricultural promotion that proves to be obscure This paper conducted an investigation on modal values ​​based on Halliday’s systematic modality theory. Corpus quantitative research approach was used in the hope of gaining more insights into agriculture technique English. A comparative analysis was made between Brown Corpus and agricultural This Corpus One contains 400 000 words, summarizing the differences in application of modal verbs across the two corpora. This study aims to probe into modal values ​​in a way that agricultural technology promotion texts in a way, which could be be better understood by readers of target language.