* Q2 net 7.82 bln yuan vs 7.39 bln yuan poll average
* Writes down 382 million yuan in fair value
* H1 premiums up 13 percent to 183.6 bln yuan
* China Life shares underperform benchmark in Hong Kong (Adds analyst comment, background)
By Michael Wei and Doug Young
BEIJING/HONG KONG, Aug 25 (Reuters) - China Life, the world's top life insurer by market value, warned of more market uncertainty ahead after second-quarter profit fell 27 percent amid write-downs in a weak stock market.
The company and its top domestic rival, Ping An Insurance , which reported on Tuesday, took hits from stock market investments and have flagged a possible slowdown as China tries to cool its racing economy.
But unlike China Life, Ping An's diversification into other financial products, including banking, helped to shield it from the worst effects of the stock market downturn.
Chinese insurers' weak equity investments have offset a steady increase in premiums as the country's economy, which is now the world's second biggest, continues to expand.
The outlook for capital markets remains unclear, putting relatively big pressure on China Life's investment return target, the Beijing-based group said in a filing to the Shanghai stock exchange.
"The second half looks even worse than the first half not only for China Life, but also for all Chinese financial companies as Beijing continues to fine tune its economy," said Chen Xingyu, analyst with Phillip Securities.
China Life posted a profit of 7.82 billion yuan ($1.15 billion) in the April-June quarter, its third-best quarter since 2008, versus 10.66 billion yuan a year earlier, according to Reuters calculations based on the stock exchange filing.
Five analysts surveyed by Reuters had on average forecast a profit of 7.39 billion yuan for the quarter.
"The big theme in the second half will be macroeconomic adjustment," said Chen, who has a "hold" recommendation on China Life in the short run.
Shanghai's stock market, on which China Life depends for a sizeable portion of its investment income, has fallen 17.8 percent this year. The index has rebounded 12.3 percent since July, but any gains from that period won't be reflected until the second half.
China Life booked 382 million yuan in losses from changes in fair value following the Shanghai stock market sell-off.
Gross written premiums and policy fees rose 13 percent to 183.6 billion yuan in the first half. Its gross investment yield stood at 2.51 percent in the half.
China's move to introduce new rules that would let insurers invest as much as three times their previous limit in overseas capital markets is likely to help over the longer term as companies become increasingly adept at managing their premiums.
Such a relaxation will allow China Life and Ping An to diversify from their core Shanghai stock market, notorious for its volatility and susceptibility to retail investor whims.
China Life had reported a 56 percent jump in its investment income in the first quarter of this year to over 18 billion yuan ($2.65 billion), but few expected it to repeat that feat in the April-June quarter due to the stock market slide.
For Chinese insurance companies, year-on-year comparisons may be distorted by accounting changes as Beijing introduced new rules for insurers late last year designed to bring standards more into line with global norms.
Hong Kong-listed shares of China Life are down about 15 percent so far this year, lagging a 5.6 percent decline on the benchmark Hang Seng Index. ($1=6.796 Yuan) (Editing by Muralikumar Anantharaman and Michael Shields)