The field experiment was conducted at Spices Research Centre, Shibganj, Bogra, Bangladesh during May 2015 to April 2016 to study the seasonal impact on the population density of the gall mite, Aceria doctersi within the leaf galls of Cinnamomum tamala. Bay leaf line BL001 were used for the study. Phenological studies were carried out on galled leaf samples collected randomly from C. tamala. Galled leaves were collected monthly, through random sampling and galled leaf samples were put in polythene bags and transported to the laboratory for further observation under the stereomicroscope. The maximum number of mite per gall (78/gall) with gall size 3.0cm was recorded during the month of April then it becomes gradually decrease and the minimum number of mite per gall (10/gall) with 2.1 cm gall size was recorded during the month of December. The highest Chlorophyll Concentration Index of the leaf (64.80) was also recorded from the month of December while the lowest (41.20) Chlorophyll Concentration Index of leaf was recorded from the month of April. Mite population were positively correlated with average temperature (r=0.4475) and negatively correlated with relative humidity (r= -0.5366) and rainfall (r=-0.0685). Mite population was also positively correlated with the percentage of leaf area damage (r=0.8585**).