Survival changes in morphology, photosynthetic pigments,cellular protein carbohydrate content of 2 cyanobacteria species Tolypothrix bouteillei and Mastigocladus laminosus in response to different temperature of heat stress was investigated. T. bouteillei was more tolerant to high temperature than M. laminosus as evidenced by almost two fold increase in chlorophyll-a content at 550C and increase in carotenoid content. Both the organisms cellular carbohydrate content decreases with increase in temperature after exposure to heat,after 7 days showed recovery of carbohydrates due to increased amount of carbohydrates in both state. Morphological observation showed intact cells in filaments of Mastigocladus sp. with higher pigment content with high temperature up to 550C, whereas in T. bouteillei filaments became fragmented and cells beaded with increase in temperature. Analysis of results showed that in M. laminosus, the branched cyanobacterium isolated from hot spring with 450C temperature, was more resistant to heat stress than that ofTolypothrix bouteillei under congenial environment. Since M. laminosus is already adapted to the stress environment.