The invention discloses LED nitride fluorescent powder and a preparation method thereof. The chemical structural formula of the LED nitride fluorescent powder is LaXbZcNd: rR, wherein L is at least one of Ca, Sr and Ba; X is at least one of B, Al, Ga, In and Tl, wherein Al is necessary; Z is at least one of C, Si and Ge, wherein Si is necessary; R is at least one of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, wherein Eu is necessary; and (a + r): b: c: d is equal to 1: 1: 1: 3. The preparation method is as follows: weighing raw materials according to the composition of the chemical formula of the fluorescent powder and the stoichiometric ratio, adding an activator, uniformly mixing in a glove box, sealing, then adopting the normal-pressure high-temperature solid-state method for carrying out multiple roasting under the protection atmosphere, and carrying out post-treatment for obtaining the LED nitride fluorescent powder. The luminescent material is characterized by good chemical stability, high luminescence efficiency and the like, and the manufacturing method is simple, pollution-free and low in cost.