In recent controlled release of pesticides has attracted the attention of researches. Controlled releases enjoys advantages such as eco-friendly, cost-effective, increase the duration of activity agrochemicals and simultaneously reduces the total amount of agrochemicals, decrease the environmental contamination in comparison to traditional methods of using pesticides. This research aimed at investigating the controlled release of pesticide thiram from poly (L-lactic-acid) nanofibers matrix. Thiram is a pesticide for fighting fungi in earth which can harm the plant’s root and make them go rotten. Thiram is also used to protect cultivated products during storage, traortation and packaging. At first, the optimized conditions for producing polylactic acid nanofibers as a matrix containing thiram were found. To electrospin polylactic acid, it is solutions of in chloroform-methanol (80-20 v/v) with concentrations of 8, 9, 10 and 11% (w/v) were prepared. The 9% concentration was found to be optimum. So, thiram was added to this solution with concentrations of 5, 10, 15, 20 and 25% (w/w) relation to the polylactic acid weight. Electrospun nanofibrous mats of polylactic acis-thiram were prepared from these solutions and investigated further. The electrospun nanofibers matrix characterized by FESEM, FTIR and XRD. FESEM macrographs showed uniformity in diameter and bead-free nanofibers could be obtained with solution concentrations of 9% (w/v). FTIR analysis indicated no interaction between PLLA and thiram. The effect of annealing on the controlled release investigated by heating the samples. XRD analysis showed a structure consisting of very small crystallites for polylactic acid before and even after annealing. XRD analysis showed also a structure very small crystallites for polylactic acid nanofibers containing thiram; however after annealing, XRD showed crystallization of polylactic acid containing thiram which was related to thiram. UV spectrophotometry was employed to study the release of thiram from polylactic acid matrix in deionized water. The results showed that the controlled released of thiram from polylactic acid matrix without annealing followed Fick mechanism, but after annealing the samples, non-Fick mechanism prevailed. It was also observed that level as well as the rate of controlled release was lower in the case of annealed samples. Baseically, it is concluded that electrospun polylactic acid nanofibers containing thiram can be used for the controlled release of this pesticide in long term periods in agriculture.