The transformation reaction of oxy compound of 1-methylcyclopentene, obtained by liquid- phase oxidation of appropriate cyclene over a catalyst Ba₃(PO₄)₂, with the volume velocity of supplying of raw materials, at temperature range of 100–395⁰C was studied. It has been established that the main products of reaction at temperature 360–380⁰C are methylcyclopentadienes-1,3 with an admixture of 2-methylcyclopentanone. At 100% conversion the obtained catalysate mainly consists of methylcyclopentadienes-1,3 with conjugated double bonds