Although standard model of gamma-ray burst afterglows or external forward shock afterglow model has been established in 1990s, some problems still open. In this paper, we extend the model by using time-dependent parameters, namely modify its represention as \(\{E(t),\epsilon_{B}(t),\epsilon_{e}(t),n(R),p\}\), where \(\{E,\epsilon_{B},\epsilon_{e}\}\) depend on time instead of as constents in the standard model. After calculating spectra and light curves and giving pure algebraic expressions, we fit a samples, with which can’t be fitted well using standard model. We find that these samples can be fitted if appropriate parameters be selected. Then we discuss the rationality of obtained parameters. By introducting of the method phenomenologically, we try to make the model used more convenient and can fit more afterglows.