The Schur-convexity and Schur-geometric-convexity of a class of symmetric functions are investigated. As consequences some new proofs of the well-known Ky Fan's inequality and Shapiro's inequality are presented, respectively. We also give another proof of a problem posted by S. Gabler in [S. Gabler, Aufgabe 830, Elem. Math. 3 (1980) 124-125]. Some interesting matrix and geometric inequalities are established to show the applications of our re...