Using the latent curve model, this study examined the influence of high school students' motivation for experimentation on changes in experimental strategies in observation and experimental activities. The constituent elements of motivation for experimentation included "expectancy of success," "intrinsic value," and "utility value." The constituent elements of experimental strategies included "understanding-oriented strategy'' and "repeat strategy." Using longitudinal data about high school students, a covariance structure analysis was conducted with motivation for experimentation as the explanatory variable and with the experimental strategies such as "intercept factor'' and "slop factor" that were extracted by using the latent curve model, as the objective variables. The results suggest the influence of "expectancy of success" and "utility value" on changes in the usage of the "understanding-oriented strategy."