Linear free energy relationship studies were made on the rates of deep oxidation of some lower olefins over a nickel oxide catalyst. Since the trend of reactivities of olefins seems to be determined by the type of allylic hydrogens and their number for each olefin, quite similar treatments as previously reported on the dehydrogenation of cyclohexanes may be applied to this case. That is, the overall rate of deep oxidation of olefin R at temperature T, υ(R, T), can be represented as the weighted sum of the characteristic rates for allylic hydrogen atoms as v( R,T)= ∑ m w( R,m)·v(m,T) where w(R, m) means the statistical factor, i.e., the number of mth allylic hydrogen (primary, secondary, or tertiary) for olefin R and υ( m, T), the rate of the mth hydrogen at temperature T. The logarithm of υ( m, T) is demonstrated to have a linear relationship with delocalizability, D r R( H), a quantum chemical reactivity index for hydrogen abstraction, as log υ(m,T) = log υ(0,T) + γ(T) · ΔD r R ( H m) 2.3RT where υ(0, T) is the rate of hypothetical hydrogen with delocalizability of 1.00 and γ( T) is a proportional constant. Furthermore, γ( T) is proved to be practically independent of temperature. This means that the preexponential factor of the mth hydrogen, υ( m,∞), is independent of the type of allylic hydrogen but its activation energy, E A( m) , decreases proportionately with D r R(H m ). Finally, the overall rates can be expressed as follows: v( R,T)= ∑ m w( R,m)·v(0,∞)· exp{−[E A(0)−λ D·ΔD r R( H m)]/ RT} where υ(0,∞) and E A(0) are the preexponential factor and the activation energy, respectively, for hypothetical hydrogen defined above and γ( T) is rewritten as γ D. Finally, the rate of deep oxidation of any olefin at any temperature can be predicted according to the above equation using the delocalizability inherent to allylic hydrogen and three parameters characteristic of the type of catalyst, i.e., υ(0,∞), E A(0) and γ D. This treatment is compatible with the tentative mechanism that the deep oxidation of olefins over nickel oxide involves an abstraction of allylic hydrogen as a rate determining step.