Different　from　the　linear　phononic　crystals,　elastic　waves　can　exhibit　more　interesting　phenomena　in　periodic　structures　with　nonlinear　properties.　By　the　active　control　action,　elastic　wave　characteristics　can　be　tuned　based　on　the　demand　in　practical　application.　This　work　discusses　the　possibility　of　the　active　control　action　on　elastic　waves　in　phononic　crystals　with　the　weakly　nonlinear　monoatomic　lattice　chain.　Based　on　the　Lindstedt-Poincare　method,　the　approximate　solution　of　the　dispersion　relation　is　derived.　Numerical　calculations　are　performed　to　discuss　the　influences　of　the　active　control　action　on　wave　propagation　properties.　In　order　to　present　the　features　of　nonlinear　elastic　wave　dynamics,　it　is　mainly　focused　on　the　effects　of　active　control　accompanied　by　the　changes　of　the　elastic　wave　amplitude,　nonlinear　degree,　hard　and　soft　nonlinearities.　It　is　expected　to　extend　the　analysis　and　design　of　new　phononic　crystal　devices　for　both　the　theory　and　application　fields.　(C)　2015　Elsevier　Ltd.　All　rights　reserved.