Convertible bonds issued in the Chinese mainland gained the most in more than seven years last week and the co-manager of a fund that returned 57 percent in 2014 said he remained bullish, even after the nation's world-beating equity rally.

The S&P China Convertible Bond Index jumped 8.5 percent in five days, as a similar corporate debt benchmark was little changed.

The index is up 15 percent since the People's Bank of China cut interest rates for the first time in two years on Nov 21. This year's best-performing bond funds in China are focused on exchangeable debt.

"We're relatively bullish," said Li Xiaoyu, the head of fixed income at Changxin Asset Management Co, which oversees 16 billion yuan ($2.6 billion) of assets including a convertible fund that topped the rankings and beat the Shanghai Composite Index's 43 percent gain.

"China's economic growth may stabilize at the current pace, which will support convertible bonds' good performance for some time in the future."

Optimism that a slowdown will be averted next year is drawing money into China's equity markets, driving a 21 percent gain in the Shanghai Composite Index over the past month, the most among 93 global indexes tracked by Bloomberg.

Stocks in China posted their biggest intraday swings since 2010 last Friday and 30-day volatility is at a one-year high, boosting the outlook that exchangeable debt holders can profit from conversions.

All of 2014's 10 best-performing bond funds in China are focused on convertible debt, with gains exceeding 55 percent, according to data compiled by Bloomberg.

Changxin Asset's Convertible Bond A and C funds gained 56.5 percent and 55.9 percent, respectively, this year as of last Friday.

According to Li, the central bank may cut its reserve requirement ratio or offer reverse repurchase agreements later this month to pump capital into banks after recent data pointed to a further slowdown and rising deflation risks.

The official Purchasing Managers Index slid to an eight-month low of 50.3 in November, figures from the National Bureau of Statistics showed.