The oriental mite, Eutetranychus orientalis Klein is an important pest of citrus in South of country, that cause damage to some kinds of citrus trees annually.In the present study, population fluctuations and spatial distribution for estimating the population density of E. orientalis were studied. The parameters of Taylor's law, Iwao, Morisita and Id index, RV and number of optimum samples (in two precision levels 0.1 & 0.25) were investigated. Sampling was carried out in direct observation on leaves at intervals of two weeks and it was on adult and non-adult. The project was conducted during the pest season from March to October. The results showed that the activity of pest was started from late March and gradually increased depending on weather conditions. Peak population happened in early May and late September. The study of spatial distribution of oriental mite based on Taylor's b coefficient for adult and non-adult was 1.2 and 1.46 respectively and so the distribution was cumulative. Iwao β coefficient was 1.25 and 1 for the adult and non-adult, according to this index, the distribution of mite two stage was Cumulative and random respectively. R2 values in the Taylor and Iwao index 0.98 and 0.81 were calculated respectively and showed that 98% of variance variations are predictable from the average variation in Taylor law. Consequently, a and b coefficients of Taylor were used for estimating of the spatial distribution and number of optimum samples. In the 16 sampling steps, the Z value of the Morisita (Iδ) and (Id) distribution index showed that the citrus oriental in most of sampling dates has cumulative distribution in every two growth stages. The number of optimum samples with an acceptable error rate of 0.25 and 0.1 for adult and non-adult stages was 28.4, 86.3 and 25.2, 98.5 respectively. It was found that with increasing precision from 0.25 to 0.1 optimum samples number would increase. Relative variation (RV) values for adult and non-adult were 11.15 and 26.48. Based on these results sampling should be done for ecological studies and management programs on adult and non-adult stage respectively.