1. The water, ash (from March to December, 1962，except July)，iodine, alginic acid and crude protein (form March to August, 1962, except July) contents of Laminaria japonica Aresch from Tsingtav were determined. The water content was rather high in young specimens, It was as high as 94.86%in March, and diminished gradually afterwards. In young specimens, the ash content was comparatively low, it was only 17.88% in March, but increased rapidly in April, declined in Augoat, and again increased in Decemher. As they grew, the iedine content increased monthly up to 1.13%in Angust, which is higloer than that reported by previous warkers.Tlee aeasonai rariativns o, crude protein content cvmparcd with those of alginic avid content hova shown an inverse tendency. 2.The seasonal variations in opt. pH, opt. temperature and the activity of catalase in Laminaria japonica Areach were studied. The verified results are shown in Figs. 2 and 3.The opt. pH of catalase was 8.68一9.18 and may he greater than pH 9.18. The opt. temperature of the catalase was 10-20℃. The seasonal changes of the temperature of the sea water had no in,luence upon the vpt.pH and the opt. temperature of catalasc. The maximum value of catalase activity in August is identical with that of the intensity of photosynthesis.