In order to understand the length and weight characteristics of Conger myriaster in the coastal water of Shandong Province, this study analyzed the seasonal and spatial variations in the body length, weight and relative condition factors of C. myriaster based on bottom trawl surveys of fishery resources conducted in October, 2016 and January, May, and August, 2017. We used the linear mixed-effects model to illustrate the spatio-temporal heterogeneity in the relationships between body length and weight. The results showed that the average body length and weight were significantly smaller in winter than those in other seasons (P<0.05), and the relative condition factor in summer was significantly higher than that in other seasons (P<0.05). Linear mixed effect models revealed that seasons and areas significantly influenced the parameter a in length-weight relationships of C. myriaster. In the optimal model, the parameter b had a fixed value of 3.27 and the parameter a ranged from 4.78×10^-4 to 5.68×10^-4 among seasons and areas, with the largest value in summer, followed by autumn and winter, and the lowest in spring. Meanwhile, a had the largest value in area Ⅲ (depth>50 m), followed by area Ⅰ (depth<30 m) and area Ⅱ (30m