Shanghai's tech-focused STAR Market achieved a stable debut with reasonable stock price fluctuations in its first trading month, underpinned by pilot market-oriented mechanisms, the Shanghai bourse and analysts said.

Share prices of all the 28 listed firms on the STAR Market, or the sci-tech innovation board, rose from their offer prices as of Wednesday's close－a month after the market started trading on July 22－and were up by 171 percent on average, the Shanghai Stock Exchange said in an announcement on Wednesday.

Behind the stock price gain was investors' high interest in the new board.

During the first trading month, daily turnover of the STAR Market was 25.4 billion yuan ($3.6 billion) on average, accounting for 13.8 percent of the total turnover of 1,500 SSE-listed firms, SSE data showed.

Investors' excitement has been gradually turning into rationality, the SSE said, citing that the percentage of shares that changed hands on the STAR Market had reduced from the 78 percent on July 22 to about between 10 percent and 15 percent.

Price fluctuations were within a reasonable range, as only four STAR stocks had hit the 20 percent daily price gain limit as of Wednesday, according to the SSE.

When the STAR Market debuted on July 22 with the first batch of 25 public firms, stock prices of the listings soared by an average of 140 percent from offer prices amid high investor spirits.

STAR stocks then registered robust gains despite the weak performance of the main board. The gain momentum was broken in the third trading week, when prices of STAR stocks fell by 10.5 percent on average, according to financial information provide Wind Info.

On Thursday, prices of STAR stocks fell by 1.9 percent on average.

"The overall performance of the STAR Market saw the full pricing-in of opinions from bulls and bears, an uptrend with fluctuations, and a return to rationality," the SSE said in the announcement.

Relaxed price fluctuation limits have enabled the STAR Market stocks to be more timely priced, leading to higher pricing efficiency than the main board, according to analysts from Shenwan Hongyuan Securities.

Securities regulators lifted price fluctuation limits for STAR stocks in their first five trading days, and thereafter a 20 percent daily price fluctuation limit is effective, versus a 10 percent limit on the main board.

Analysts expect trading on the STAR Market to become more rational in the medium term, with valuation levels to better reflect company fundamentals. Firms with strong fundamentals may sustain high valuations, while weaker ones may see a marked divergence in stock price performance.

The market-oriented initial public offering mechanism of the STAR Market, or the registration-based IPO system, also showed its effect, with the 28 STAR listings' price-to-earnings ratios of offer price varying from 18 to 269, according to SSE data.

This marked a difference from the main board, where almost all new offerings are priced at a maximum of 23 times earnings under the approval-based IPO system.

The SSE also disclosed that during the first trading month of the STAR Market, it strengthened supervision on illegal trading and dealt with eight cases of abnormal trading behavior on the new board.

Shi Jing contributed to this story.