A syntactical analysis is one of the linguistic branches which studies sentence structure. Sentence pattern becomes important since it affects the meaning of the sentence. The ambiguous meaning of the headline can be revealed by knowing its sentence structure using the tree diagram. Therefore, the researcher needs the syntactical theory and tree diagram to understand the meaning of the headline article. Based on the problem, this research that aimed to reveal the types of sentence structure found and to find out the dominant type of sentence structure in the Headline Article of Jakarta Post Newspaper edition the third week in February 2020.
The research type of this research was qualitative. The data were 40 headlines of Jakarta Post newspaper edition third week in February 2020. The source of data was gotten by accessing the Jakarta Post website under the address www.jakartapost.com. The researcher employed the theory of Chomsky to analyze the sentence pattern. Additionally, the researcher also employed the theory of OGrady, Dobrovolsky, and Katamba (1996) to represent the tree diagram and phrase-structure rules. 
Based on the result, this research found some types of sentence structure. These were the number of each type; the simple sentences were 31 headlines (77.5%), the compound sentences were 3 headlines (7.5%), and the complex sentence was 1 headline (2.5%). Besides sentences, phrases revealed as headlines as well, they appeared in 5 headlines (12.5%). The phrases are used on the headline because they were shorter and require less space, as long as the phrase covered the content of news. The dominant type was a simple sentence because it mostly appeared rather than other types. To sum up, the syntactic theory and tree diagram here were used to understand the ambiguous meaning of the headline article in Jakarta Post Newspaper edition the third week in February 2020.