Producing fully charm structures in the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>J</mml:mi><mml:mo stretchy="false">/</mml:mo><mml:mi>?</mml:mi></mml:math> -pair invariant mass spectrum

Focusing on the novel phenomenon of several enhancement structures existing in invariant mass spectrum a $J/\ensuremath{\psi}$ pair, which was reported by LHCb very recently, we find new dynamical mechanism based special reactions, where all possible combinations double charmonium directly produced proton-proton collision are transitioned into final-state $J/\ensuremath{\psi}J/\ensuremath{\psi}$. Under this framework, totally different from popular tetraquark explanation, experimental data line shape $J/\ensuremath{\psi}$-pair can be well mimicked. Since proposed is universal enough, further predict $\mathrm{\ensuremath{\Upsilon}}(1S)$-pair spectrum, may provide realistic approach to test work and form task for CMS experiments.