: The purpose of this thesis is to compare the educational effectiveness of Chemistry laboratory in second grade of high school by using the educational software and traditional method . The independent variable was teaching method and the dependent variables were attitude and knowledge. The study has been carried out using a semi-experimental method. The samples were randomly selected from high schools in Ilam city. In each school, two classes were randomly selected; one class was selected as experimental group and the other as the control group. For the former, a pre-test was done which indicated that there was no significant difference between two groups in attitude and knowledge level. Two-dimensional diagram of content–purpose related to the items of attitude questionnaire and knowledge test were presented to professors’ and experts in order to obtain the validity of the instruments. The reliability measurement of learning achievement was α= 0.71 and for the attitude questionnaire was α=0.88. According to the research procedure, the control group did the experiment in the traditional laboratory using chemical substances laboratory tools, and the experimental group did the same experiment using educational software in the computer site. Using the analysis of covariance for post-test, it was determined that the control group had more educational achievement than the experimental one, but the experimental group had more positive attitude to computer and chemistry laboratory than the control group. There were significant differences between two groups in three parts of attitude including: emotional, cognitive and behavioral.