According to some studies done during the research, ESP courses are mainly reading oriented, but in spite of these, it seems that Iranian graduated students after studying ESP courses for at least two semesters are not efficient readers and have a lot of problems related to their fields of study. In order to promote the effectiveness of such courses, the present research introduces a set of inter-lingual, intra-lingual, inter-semiotic translation tasks to be used in ESP classes, and further intends to check the effectiveness of the translation tasks in an experimental research. Since the research is an experimental one, an experiment has been done to seek support for our claim. The experiment has been done in many groups and at the end; students reading ability in experimental groups have been compared with that of control groups using t-test method of case II type. The results indicated that translation tasks were so effective in promoting ESP students` reading ability in experimental group but not so effective in the other one.