Alkyl dinitrites have attracted attention as an important type of nitrosating agent and a pollution source in atmosphere. The reactivity and chemistry of alkyl dinitrites induced by the two ONO functional groups are relatively unknown. In this work, decompositions of 1, 3-cyclohexane dinitrite and 1, 4-cyclohexane dinitrite are studied by electron impact ionization mass spectroscopy (EI-MS). Apart from NO+ ($m/z$=30), fragment ions $m/z$=43 and 71 are the most abundant for the 1, 3-isomer. On the other hand, fragments $m/z$=29, 57, 85, and 97 stand out in the EI-MS spectrum of 1, 4-isomer. Possible dissociation mechanisms of the two dinitrites are proposed by theoretical calculations. The results reveal that the ring-opening of 1, 3-cyclohexane dinitrite mainly starts from the intermediate ion (M-NO)+ by cleavage of two $\alpha$C-$\beta$C bonds. For 1, 4-cyclohexane dinitrite, in addition to the decomposition via intermediate (M-NO)+, cleavage of $\beta$C-$\beta$C bonds can occur directly from the parent cation M+. The results will help to understand the structural related chemistry of alkyl dinitrites in atmosphere and in NO transfer process.