In this paper, we introduce the concepts of subalgebras, principal subalgebras and $$d_{L}$$
d
L
-subalgebras of a principal MS-algebra and describe the lattices of such subalgebras. Also, we describe a subalgebra [S] that generated by a subset S of an MS-algebra (principal MS-algebra) L and study related properties. Finally, we determine and characterize the principal subalgebras of a principal MS-algebra via admissible pairs.