Provided is a method for radon gas release concentration in-situ determination in underground different position coal rock beds. The method comprises steps: determining underground different position coal rock beds for radon gas release concentration determination, and respectively numbering as L1 to Ln; automatically calibrating a determination coefficient of a continuous radon measurement instrument (7); fixedly arranging a cylindrical hollow rubber piston (3) on the end of a plastic flexible pipe (4), putting the cylindrical hollow rubber piston in an exploration drilling hole (2); when measuring the radon gas release concentration in the L1, recording data after measurement of each hour, continuously measuring for 3 hours, to record obtained three pieces of data respectively as C11, C12, and C13, taking the average value of the C11, C12, and C13 as the radon gas release concentration in the L1, recording as C1; measuring the L2, L3, and the like, Ln in sequence, and respectively recording the final measuring result as C2, C3, and the like, Cn. Using the method, radon gas release concentration determination of all position coal rock beds can be completed in the existing exploration drilling hole, interference on measuring results by size effect and external environment factors is eliminated, and field in-situ determination is actually realized.