一般认为，这个需要大写。
In Titles: Do Capitalize

Nouns (man, bus, book)
Adjectives (angry, lovely, small)
Verbs (run, eat, sleep)
Adverbs (slowly, quickly, quietly)
Pronouns (he, she, it)
Subordinating conjunctions (as, because, that)
In Titles: Do Not Capitalize

Articles: a, an, the
Coordinating Conjunctions: and, but, or, for, nor, etc.
Prepositions (fewer than five letters): on, at, to, from, by, etc.

非关键主词，不大写更明确