Aim\ To obtain the relation between output pressure of explosive and time under the condition of two dimensional explosion. Methods\ A \%p-t\% relationship between output pressure of explosive and time under the condition of two dimensional explosion is derived. The numerical calculation of \%p(t)\% relation between the booster pellet and the medium was made as an example. The theoretical results are compared with the experimental results.Results\ Experimental data well conform with the theoretical prediction

within 7%. Conclusion\ The theoretical results can be used for numerical calculation of \%p t\% relation for engineering use.