Abstract: The invention discloses a red phosphor powder which is based on strontium (Sr) aluminate and using europium (Eu) as exciting agent, and is characterized by that its chemical equivalence formula is (SrO)4(?Me+2O)1Al2O3: Eu, wherein Me+2=Mg and/or Ca and/or Ba. The present invention also discloses a manufacturing process for the red phosphor powder and a warm white light-emitting diode employing the phosphor powder. Moreover, the present invention also discloses a multi-layer polyethylene thin film using the red phosphor powder.