No, Deuteronomy 6:4, also known as the Shema1 , does not disprove the Trinity. The Trinity is the teaching that in the one God there are three distinct, simultaneous, co-eternal, and co-powerful persons known as the Father, the Son, and the Holy Spirit. Deuteronomy 6:4 says that God is one LORD. The word "LORD" in Hebrew it is YHWH (Yahweh, or Jehovah). The verse is saying that YHWH alone is God and is teaching monotheism. The verse is not about God being the Trinity though He is. It's about only being one God. The Shema is a statement about monotheism and the Trinity monotheistic. Also, the word for "one" in Deut. 6:4 is "echad," which often used for describing a composite unity such as one cluster of grapes.
However, some will respond by saying God is one, not three. But the verse does say that God is "not three." It says God is one. Okay, one what? One God! This is what Deut. 6:4 says, and the Trinity doctrine agrees, there is one God.
"This confession of monotheism does not preclude the biblical doctrine of the Trinity. ”God“ is plural (elohim), possibly implying the Trinity, and one (echad) may suggest a unity of the Persons in the Godhead (cf. Gen. 2:24, where the same word for ”one“ is used of Adam and Eve).2