To further reveal the reactivity of cyclopropenylidene with R-H compounds, mechanisms of four reactions between cyclopropenylidene and R-H (R= F, OH, NH2, CH3) have been systematically investigated employing the second-order Moller-Plesset perturbation theory (MP2) method. Geometry optimization, vibrational analysis, and energy property for the involved stationary points on the potential energy surface have been calculated. All the mechanisms of four reactions are identical to each other. Based on the calculated results, there are three steps (step a, b, and c) along the reaction between cyclopropenylidene and R-H. For the first step, cyclopropenylidene is inserted into R-H to form an three-membered ring intermediate. For the second step, the three-membered ring is opened to form a carbene intermediate. With regard to the third step, it is H-transfered processes, the ultimate product is alkyne.