High performance liquid chromatography was used to analyse the content of Cucurbitacin B (CuB) to study the chemical communication relationship between Aulacophora femoralis chinensis Weise and Cucurbita moschara (Duch.) Poir. Both pest damage and mechanical damage resulted in the change of CuB content in the cotyledons of squash fluctuated around the CuB content in the uninfested or undamaged plants, but the changing trends of CuB content resulted from the beetle damage and mechanical damage were quite different in three aspects. Firstly, the velocity of induction reaction by the beetle was faster, comparing with mechanical damage. For instance, the CuB content in the beetle-infested plants had already distinctly increased after 1 h foliage disposal, but it is 0.5 h later in the mechanically damaged plants. Secondly, the inducing CuB content in beetle-infested plants was much higher than that in the mechanically damaged plants. Lastly, the duration of induction reaction in beetle-infested plants persisted much longer than that of the mechanically damaged plants. The reaction could last 160 h in the beetle-infested plants, however, it was only 80 h in the mechanically damaged plants. Furthermore, even if we dealt the stems with the pest damage or mechanical damage, the CuB content in the cotyledons of squash changed similarly to that in the foliage disposal. That demonstrated the release of CuB in the beetle-infested plants or mechanically damaged plants was systemic. At the same time, the uninfested or undamaged cotyledons had higher CuB content than that in the infested or damaged cotyledons in the same individual plant.