Ammons often writes in two- or three-line stanzas. Poet David Lehman notes a resemblance between Ammons's terza libre (unrhymed three-line stanzas) and the terza rima of Shelley's "Ode to the West Wind." Lines are strongly enjambed. Some of Ammons's poems are very short, one or two lines only, while others (for example, the book-length poems Sphere and Tape for the Turn of the Year) are hundreds of lines long, and sometimes composed on adding machine tape or other continuous strips of paper. His National Book Award-winning volume Garbage is a long poem consisting of "a single extended sentence, divided into eighteen sections, arranged in couplets".
Many readers and critics have noted Ammons's idiosyncratic approach to punctuation. Lehman has written that Ammons "bears out T. S. Eliot's observation that poetry is a 'system of punctuation'." Instead of periods, some poems end with an ellipsis; others have no terminal punctuation at all. The colon is an Ammons "signature"; he uses it "as an all-purpose punctuation mark."
The colon permits him to stress the linkage between clauses and to postpone closure indefinitely.... When I asked Archie about his use of colons, he said that when he started writing poetry, he couldn't write if he thought "it was going to be important," so he wrote "on the back of used mimeographed paper my wife brought home, and I used small [lowercase] letters and colons, which were democratic, and meant that there would be something before and after [every phrase] and the writing would be a kind of continuous stream." 
According to critic Stephen Burt, in many poems Ammons combines three types of diction:
- A “normal” range of language for poetry, including the standard English of educated conversation and the slightly rarer words we expect to see in literature (“vast,” “summon,” “universal”).
- A demotic register, including the folk-speech of eastern North Carolina, where he grew up (“dibbles”), and broader American chatter unexpected in serious poems (“blip”).
- The Greek- and Latin-derived phraseology of the natural sciences (“millimeter,” “information of actions / summarized”), especially geology, physics, and cybernetics.
Such a mixture is nearly unique, Burt says; these three modes are "almost never found together outside his poems".
As far as topics often addressed by Ammons, those of religious and philosophical concern are visited in his works as are many scenes involving nature, almost in a Transcendental fashion. According to Daniel Hoffman, who wrote a book review on Ammons, stated that his work "is founded on an implied Emersonian division of experience into Nature and the Soul," adding that it "sometimes consciously echo[es] familiar lines from Emerson, Whitman and [Emily] Dickinson."