The present invention provides a SAPO-34 molecular sieve, whose chemical composition in the anhydrous state is expressed as: mDGA.(SixAlyPz)O2; wherein DGA is diglycolamine, distributing in the cages and pores of said molecular sieve; m is the molar number of the template agent diglycolamine per one mole of (SixAlyPz)O2, and m is from 0.03 to 0.25; x, y, z respectively represents the molar number of Si, Al, P, and x is from 0.01 to 0.30, and y is from 0.40 to 0.60, and z is from 0.25 to 0.49, and x+y+z=1. Said SAPO-34 molecular sieve can be used as an acid-catalyzed reaction catalyst, such as a methanol to olefins reaction catalyst. The present invention also concerns the application of said SAPO-34 molecular sieve in adsorption separation of CH4 and CO2.