In the present investigation the analysis of phytochemical constituents from Halodule pinifolia were determined. The seaweed Halodule pinifolia were collected from Mandapam coast of Rameshwaram, Tamilnadu, India and the standard methods were followed for extraction of phytochemicals from the seaweed. The secondary metabolites synthesized from seaweeds and the broad spectrum of biological activity. The analysis of proximate content of Halodule pinifolia with methanol and hexane solvents was individually determined. Among the two extraction solvents, the methanol with Halodule pinifolia showed excellent results when compared with hexane solvent.The proximate contents like moisture (16.14mg/g), Ash (3.35mg/g), insoluble ash (3.14mg/g), fat(3.60mg/g), crude fiber (3.37mg/g) and N2free extractives (3.43mg/g) recorded from methanol extract of Halodule pinifolia and hexane extract showed moisture (8.03mg/g) Ash (6.73mg/g), insoluble ash (3.92mg/g), fat (4.02mg/g), crude fiber (4.12mg/g) and N-free extractives (2.23mg/g) recorded in the seaweed whereas qualitatively and quantitatively phytochemicals like alkaloids, saponins, flavonoids, tannin, phenol, steroid, terpenoids, protein, anthroquinone and reducing sugar were analysed in both solvents of methanol and hexane of Halodule pinifolia extracts. The effect of Halodule pinifolia seaweed organic fertilizer with different concentration like 200 to 800mg/g treated in each pot experiments of Benincasa hispida. The maximum concentration 800mg/g seaweed liquid showed excellent performance for the growth and development of Benincasa hispida.