Fortescue Metals Group has led the Deloitte WA index up 4 per cent in August after the barometer surged 9 per cent in July.
At the end of last month, the capitalisation of WA top 100 ASX-listed companies was $142.9 billion.
FMG's shares rose 42.4 per cent over the course of July and August on the back of a much-needed increase in iron ore prices.
Deloitte Perth Lead Audit Partner Tim Richards said the index's increase was driven largely by a recovery in commodity prices as a result of positive Chinese economic data.
"The Chinese economy is transitioning to an economy that is driven by domestic consumption, as local demand in China increases rapidly," Mr Richards said.Other big movers for the month of August included gold miner Saracen Mineral Holdings (up 71.9 per cent), Texas-based oil and gas company Lonestar Resources (up 47.1 per cent and engineering contractor Calibre Group (up 45.1 per cent).